oh fug thats a tough call.
"favorite" is pretty broad.
i cant put them in any particular order but i'll have to go on how much i've replayed it, how well it still holds up, how much fun it is, and how much of a personal attachment i have to the game.
i know these games are not the best; theyre just favorite games of mine.

1. Panel de Pon / Tetris attack (SNES)
2. MGS2 (PS2)
3. Harvest moon back to nature (PSX)
4. Sim City (SNES)
5. Sim Ant (SNES)

Theyre not all paticularly the best games, but they're games i love and i've played endlessly, and would still play, and i would defend them and all of their flaws endlessly in a biased and autistic manner.