According to Wikipedia Cyclops, Rogue, Sabretooth, Storm, Wolverine, Akuma, Cammy, Charlie, Chun-Li, Dhalsim, Ken Masters, M. Bison, Ryu, and Zangief are all the playable characters in the game.
On the wiki fandom page for X-men vs. Street Fighter page it says that Gambit, Juggernaut, Magneto, Apocalypse, and Akuma (Gouki) are also featured in the original 1996 version.