I found the disassembly/decompilation/source code for the following games:
Sonic 1, Sonic 2, Sonic 2 SMS, Sonic 3 & Knuckles, Sonic the Fighters, Sonic Adventure DX, SRB2, SRB2K, Super Smash Bros. Melee, Naruto GNT4, Footsies
How hard would these be to port over? and uh, how does it work?