I might argue that Samus Aran would qualify as "transgendered" in a similar sense that the Final Fight character does, while Samus is both more well known and popular than Poison.
Samus was created during the old school Nintendo days, when practically all video game protagonists were male. Samus wears a full-body combat suit with an opaque faceguard built into her helmet. There is not an inch of Samus's body visible during normal gameplay.
In the original Metroid game, Samus would remove parts of her suit at the end of the game if you completed the game in a certain amount of time. This allowed the faster players to realize that Samus is, in fact, a woman. At the time this was a very surprising discovery, as Metroid was one of the first games to feature a female protagonist.
To this day, many casual gamers who are unfamiliar with the Metroid games still consider Samus to be male. With the addition of "Zero Suit Samus" to Super Smash Brothers Brawl, this misconception will probably become less common over time.
Samus could be compared to a "crossdresser" because, at the time, all other futuristic combat-suit wearing heroes were male.
