These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Contemptible Cover: The original SNES port features a cover that is naught but a blank background and an extreme close-up shot of Haggar and a burly Leatherman thug, possibly meant to be Abigail, eyeballing each other. It sends a somewhat different message of what the game is about than Capcom USA probably intended.
Poison. Fans wanted her to cross to the Street Fighter series so badly, they kept asking producers to put her in the games.
Epileptic Trees: Thanks to an official artwork of Lucia doing aerobics with Chun-Li, the fact that both are detectives, and the resemblance of her moves to Chun-Li's signature Hyakuretsu Kyaku, it's been implied that Lucia may have trained under Chun-Li or is even friends with her.
This is justified, as it's somewhat normal for Japanese companies to outsource their unpopular-in-Japan franchises to Western studios, so they can do whatever they want with them. In this case, it backfired really bad.
Gamebreaker: Final Fight One has Street Fighter Alpha versions of Guy and Cody to unlock. While not that much different, their stats are tweaked compared to the originals. Alpha Guy still has the same speed and attack power, but takes far less damage from most attacks. Alpha Cody on the other hand while he has the same speed, he takes a bit less damage than normal and dishes out far more damage. Either one will make the game pretty trivial.
Good Bad Bugs: You can force Edi.E to go it alone by not scrolling to the end of the stage. Makes the fight with him almost too easy.
Porting Disaster: The SNES port of the first game was a borderline case. In terms of sound and graphics it was very close to what the arcade game offered (some even prefer the SNES soundtrack over the arcade original, which used rather harsh instrumentation). On the other hand, Guy (or Cody, depending on the version) was missing in action, there was no two-player mode, one of the levels was left out, and there were generally fewer enemies on the screen at any given time than there were in the arcade version, which messed up the game's balance somewhat. The bowdlerization didn't really help either.
The Woobie: Vanessa, after her brother is killed and her bar goes up in flames.
Viewer Gender Confusion: Much of the confusion of Poison's gender comes from Poison and Roxy's exclusion in the overseas SNES version of Final Fight. Final Fight Revenge, an American-designed 3D fighting game, adds further confusion as Poison was depicted as born female. The Japanese localization reverted back to her birth sex. Roxy's gender is classified "female" in the character bios of Capcom Classics Collection Vol. 1, but this is nothing but a retcon by Capcom USA.
Adding more fuel to the fire, not even Capcom Japan seems to remain consistent on what they are- the fact both are depicted as having very large breasts, general female shapes and Poison being voice acted by a woman in modern games aren't really helping matters, either.
Also weather or not Poison is pre or post Sex reassignment surgery for those who agree she's transgender.