They'd be hard-pressed to get Final Fantasy VII on a 128-megabyte cartridge. It may not be impossible, but it would require so much dedication and work.
Resident Evil 2 had a lot going for it:
-The two PSX discs had more data alike than differences, meaning that only one copy had to be on the Nintendo 64 cartridge
-The fact that it WAS only two discs rather than more (which, again, shared most information)
-The programmers manually compressed each background and video for Resident Evil 2 on Nintendo 64; the process wasn't automatic
-The videos on the Nintendo 64 version were extremely grainy, and the sound was even worse