We'd have a much smaller roster if they tried to redo all the characters with the time given to them. (ShonenGameZ.com)
The PS3 has a few exclusive classic characters too, leaving the 360 version with a comparatively small roster. (nosleepgamer.com)
The characters are pretty different from one another, but there are only about 24 in the game, a much smaller roster we have come to expect in modern games. (darkstation.com)