NamcoXCapcom

From the upper left, top to bottom, left to right:
Darkstalker: Morrigan
Ghouls'n Ghost: Arthur
Street Fighters: Cammy
Street Fighters: Ryu
Tower of Druaga: Gil
Genji and Heike Clans: Yoshitsune
Shadowland: Tarosuke (I think that's his name)
Darkstalker: Demitri
Tekken: Heihachi Mishima
Tekken: Jin Kazama
Tales: Leon (Judas in-game)
Original: Reiji
Captain Commando: Captain Commando
Captain Commando: Baby Commando
Strider Hiryuu: Strider Hiryuu
Legend of Valkyrie: Sabine
Tales: Stahn
Tales: Rutee
Street Fighters: Sakura
Original: Xiaomu
Legend of Valkyrie: Valkyrie
Street Fighters: Chun Li
Street Fighters: Karin
Xenosaga: M.O.M.O.
Street Fighters: Ken
Legend of Valkyrie: Cirno
Captain Commando: Ninja Commando (Sho)
Xenosaga: KOS-MOS
Xenosaga: Shion
?????: ......er, don't know the game in English. She's a vendor.
Final Fight: Guy