This is just me noodling around with the rosters and discussing how much I like (or don't like) the various characters and why. Not sure how this will play out. I suspect I'll get the first Street Fighter game done. As we get further along, the rosters get significantly bigger, but they also feature significantly more repeat characters that I won't have to redress again and again. Chances are I'll be able to get two games in most posts at some point. When I'm done, I'll switch to either Fatal Fury or King of Fighters and do the same thing.
I. Street Fighter I introduced us to the original playable characters, Ryu and Ken (and for years, we pronounced it RAI yoo like Ryan with a different second syllable, in this and other games that used the same name, before spergy, weeaboo nerds and beta nitpickers had to try and "correct" us by saying REE oo or ree YOO or however exactly they pronounce it. Which is equally incorrect from a Japanese standpoint, I'll note, but I don't care—I don't speak Japanese, nor do I care to. In English, it was always RAI yoo, and it will remain so to me.) In retrospect, they don't seem like the most auspicious of characters, but when you're pioneering an entire genre, you can get away with fairly vanilla designs, because they haven't been done before. When the fourth or fifth game in a row tries to make copycat Ryu and Ken characters, that's lame, but when the first one does it, they become icons.
None of the other characters were playable, of course, so in some sense they don't count. However, many of them have become playable over time, so they're worth bringing up. When playing you must pick either Japan or the USA as your first country to go to. If you go to Japan, you face Retsu and Geki. Retsu is the iconic cloistered monk martial artist, which is a stereotype that dates back to early Hong Kong cinema movies of the 70s at least, if not even earlier. He's never appeared in anything else, doesn't even have any special moves that I can remember, and is pretty non-memorable, even given the context in which he appeared. They've tried to link him to various characters in the backstory by saying he was friends with Gouken or Oro or Dhalsim, and that he was excommunicated from his temple (which is curious, since that's his stage) but none of those appear in the game, and they feel like much later after the fact desperate attempts to make him interesting. Geki appeared on the shores of a lake or bay with Mt. Fuji in the background at sunset, and was a pretty classic 80s ninja, with throwing stars and everything. Today, the 80s is far enough away that it probably feels like a foreign country to people who didn't live through it, so you'll have to take my word for it that the 80s and ninjas had some major mojo together, which always made Geki mysterious and cool. It's a bit of a shame that he's never really made any other appearance except in non-canonical comic books and mangas, etc. Not only did he throw stars, but he had a claw-like weapon (less dangerous looking than Vega's, though) and could teleport very short distances. All part of the Shinobi mystique of the 80s. And maybe that's why he hasn't reappeared. He's kind of a dated, frozen piece of 80s pop culture, even in Japan, I suspect.
If you picked the US, on the other hand, you fought Joe and Mike. Joe was extremely anonymous; he's a blond spiky haired guy, like a potato-faced Billy Idol. He's got red pants and sneakers, and is shirtless. It's believed that he's based on Benny "The Jet" Urquidez, who was a popular competitive martial artist. Joe features Benny's real life signature move, a spinning reverse kick, as his only special move. He may also be based on the kickboxing legend Joe Lewis, who was supposed to appear with Bruce Lee instead of Chuck Norris in Way of the Dragon, but couldn't due to a scheduling conflict. (He actually beat Norris in at least one championship. He's considered the father of martial arts in the West.) But all that backstory aside, and we certainly didn't know any of that in 1987, he's just kind of a boring character. Mike was clearly based on Mike Tyson, although he just wears a red t-shirt and faded blue-jeans with tennis shoes. Although his story and appearance are almost identical to that of Balrog, Capcom have always insisted that he is not the same character. However, in SFV, one of the alternate costumes for Balrog is called "Mike-like" and he looks just like him. If you play the SFI version of arcade mode, he's one of the characters you could face as well.
After beating both of those countries, you have to pick again between China or Britain. If you go to China, you face Lee, a character who's never appeared again. While probably based on Hong Kong cinema characters like Li Shuwen or Beggar So, he comes across as just a generic Chinese guy to Western audiences. Again, Capcom have referred to him obliquely here and there in the backgrounds of almost every other Chinese character (apparently only about half a dozen people live in China, and they all know each other or are related) but this comes across as special pleading. Gen is the other character you fight after him, and this is the same Gen as appears in the Alpha series and Street Fighter IV and a brief cameo in Street Fighter V. His design is based on a very popular martial arts movie character (in turn based on a historical figure, but his interpretation here is much more informed by the movies) from several movies from Hong Kong, Bak Mei. Of course, he's developed more on his own within the Street Fighter franchise, but he's always hewed close to his source material in many ways. His pressure points Fist of the North Star type kung fu is also heavily influenced by cinema and manga, making him a bit of a classic of Oriental entertainment. Granted, you don't see a lot of that in the first game; it comes out more in the Alpha series. In typical "lost in translation" fashion, the fact that he's a serial killer and gang member doesn't mean that he's not a hero to Oriental audiences, something which Udon has occasionally struggled to reconcile in their comic book interpretation of the story, in which he had to be a criminal "in remission" who Chun-Li berates for his criminal past. No such vibe was present in the original, because hey! Surprise, surprise: diversity means actual difference and Oriental audiences have a different moral compass by which to judge his actions than Western audiences.
If you go to England, on the other hand (or after you've defeated China, when you have to go to England) you'll face Birdie and Eagle (no idea if the avian theme was on purpose or not. Or maybe it's a reference to golf.) Birdie has appeared in three subseries, and changed his appearance drastically in that time. In the first game, he's a white guy; a pretty typical punk from the English punk rocker scene from the late 70s or early 80s; tall, muscular, clad in leather and and with a blond mohawk. For some reason when he appears in the Alpha games, he's been race-swapped and is now a thick-lipped black or maybe high yellow man with a super-exaggerated and physically impossible mohawk with a hole in the middle of it, and bizarre mutton-chops. His signature move gradually becomes throwing out chains and grabbing you with them and slamming you around, while in the first game he only uses them sparingly in a single grab and squeeze move. By the time SFV rolls around, he's become extremely overweight and gross and is played for grotesque comic relief in a way that is typical for Asian entertainment, but which doesn't translate very well to the West. Eagle, on the other hand, is a butler who uses two nightsticks, or side-handled batons. Sometimes they're called escrima or tonfas, but in nitpicky fashion, those are not all exactly the same thing (although very similar) and given his British background in the 80s, I think the nightsticks make the most sense (although given that Capcom is a Japanese company, maybe the tonfas do.) He was originally intended to be an homage to a bodyguard character from Fist of Fury, but he seems to have migrated with his minor appearances in CvS2 and the handheld SFA3 game to being more clearly based on Freddie Mercury. Sort of. His more elegant dress and appearance is supposed to be a counterpoint to Birdie's cockney punk appearance. Either way, the Japanese interpretation of the English doesn't seem particularly flattering.
Finally, if you beat all eight fighters at all four of the countries, you travel to Thailand, where you face the final two: Adon and Sagat. Both are fairly well known; Adon also appeared in the Alpha games and SFIV, although he looks pretty different, and Sagat appears in every SF series except III (and, as far as we know, VI, although that's not out yet at the time of this writing.) Both are meant to be Thai Muay Thai boxers. However, it's worth noting that neither one of them look very much like an ethnic Thai. Adon would be abnormally large for a Thai; he's bigger than Ryu and has spikey red hair. He dresses like a traditional Muay Thai boxer; shorts, wrapped wrists and ankles, no shirt, and with a headband. In later appearances, this spiky hair turns into a bizarre flattop that looks like an ironing board, but it remains red, or even more orange-ginger like the Weasleys. If Adon is big, red-headed and white-skinned for a Thai, Sagat is even more freakish. At supposedly 7'5" and quite lean, muscular and healthy (i.e., doesn't exhibit the side effects of gigantism), he's a freak of nature for any population group, especially the notoriously short and slight Thais. Although normally bald and somewhat brown-skinned, there are some alternative costumes that show Sagat with reddish-brown hair. I'm not sure what to make of all of that other than that Capcom and/or the Japanese in general don't really care about ethnicity at all, or their art style just kind of ignores it. Sagat also has solid white eyes in most appearances. Or eye, rather; he has a patch over one eye, of course. Sagat's an interesting character; he went from being a pretty one-dimensional "I just want to be the strongest" boss in SF1 to becoming an angry mobster who wants revenge in SF2, to gradually becoming a more honorable rival to Ryu, who felt really pushed by Ryu's own skill to becoming much better himself in later games (even Alpha, which is a later game than SF2, but which takes place earlier.) By SFV he's ended his association entirely with Shadaloo, and his place as one of the three lieutenants to Bison is taken by F.A.N.G. instead. This was good character development for Sagat, but of course, F.A.N.G. is literally one of the worst characters ever developed for SF, so we lose otherwise. The rehabilitation of Sagat is a curious one, because it seems that with Street Fighter in general, over time, they are reluctant to make any character too evil. Even Akuma has some redeeming moments. Bison seems to be the only one immune to this treatment, but a lot of other former villains end up being simply rivals over time. SNK has done something similar with a number of Fatal Fury and King of Fighters characters; Billy Kane being a notable example, or even Iori Yagami.
For the most part, the characters that never really left the SFI realm: Joe, Mike, Retsu, Geki, Lee, and Eagle belong in that left behind pile and its probably good that they looked for more inspiration elsewhere. Eagle maybe had some potential, and Geki is one that I've always had a little bit of interest in, being a much more iconic shinobi character that anyone else in the series, including even Ibuki and Guy. They could have maybe gone somewhere, but didn't. Sagat is a total winner as a character; there's nothing not to like about him. Adon and Gen are... OK although it really took Gen's strange rivalry with Akuma to make him pop. And, of course, Ryu and Ken are iconic and over time have developed into really interesting characters with the time and attention they've gotten over the years. Birdie started off fairly generic, and actually got worse with time, to the point that I actively dislike the character now, and feel kind of irritated with what they've done to him, especially in the jump from Alpha to V.