Here's my current list of things:
Obvious Extras:
Burning Rangers - Wavs and wallpaper
Christmas Nights - Wallpaper
Nights into Dreams - Wallpaper
Sonic Jam - Wallpaper
Ten Pin Alley - The King James bible is in the /Readme and wallpaper in /Bonus
Widescreen Support:
Batman Forever - The Arcade Game (?)
Battle Arena Toshinden Remix
Battle Arena Toshinden URA
Burning Rangers
Clockwork Knight
Clockwork Knight 2
Command & Conquer
Croc - Legend of the Gobbos (?)
Cyberia
Darklight Conflict
Daytona USA
Daytona USA Championship Circuit Edition
Enemy Zero
Fighters Megamix
Fighting Vipers
Vertical/Horizontal Support:
Galactic Attack - Set to "arcade mode"
Also, with the widescreen support, i think actual hardware verification will be required to make sure SSF isn't improperly settings the resolution. SSF shows some games as4:3, 16:9, and some are a "bigger" 4:3.
So if anyone wants to chime in that would be great since i dont have a saturn anymore