When in arcade mode have a second player press start, select a character and beat them. Now the game will no longer make you fight that character. This will work againest everyone but M. Bison. Doing this will not let you unlock achievements.
I Got Next (5) = Play a match in the online quarter mode.
World Champion (15) = Compete single-player arcade mode.
Perfection (5) = Clear a perfect match in default difficulty or higher single player Arcade mode
Perfect World Champion (30) = Clear Arcade mode without losing any rounds
Hyper World Champion (25) = Clear Arcade mode without losing any matches
Bonus Bonanza (10) = Clear the perfect bonus round in single player Arcade mode
12 World Warrior (5) = Fight all 12 opponents in single player Arcade mode
7 Stars (20) = Clear single player Arcade mode in highest difficulty level
50 Token (20) = Play 50 ranked online matches
30 ranked online victories (35) = Win 30 times in ranked online matches
10 ranked online victories (20) = Win 10 times in ranked online matches
10 Token (10) = Play 10 ranked online matches
In any mode, highlight a character and press B. You should be playing in a costume from Street Fighter II: The World Warrior and Street Fighter II: Championship Edition
Note: M. Bison has his red and blue as his default suit. So you will be playing in a gray costume instead.