Alternately, you can access all the hidden characters except Red Demon and Young Athena on the character selection screen by holding R1 over the four top characters of the inner most rows of both sides. The following characters can be accessed by holding R1 while on the standard character's location at the selection screen:

Kyo: Geese
Terry: Mars People
Ryo: Goenitz
Kim: Evil Iori
Kasumi: Shin Mr. Karate
Ryu: Zero
Chun Li: Demitri
Dhalsim: DaN
M. Bison: Violent Ken
Vega: Shin Akuma