Xbox: Knights of the Old Republic /KotOR2
PS2: Final Fantasy 12, Timesplitters 2 (dependant on liking bot challenges, rubbish story), Resident Evil: Code Veronica,
PS1: Resident Evil 1-3
Thinking outside the Box:
If you can get a Gamecube cheap (which you can) I suggest the two Cube Metroid Primes. They're unique as far as gameplay goes and really well put together. Plus you'll take about 30 hours for each one.
The Resident Evil 1 remake (the greatest game remake ever by miles) and Resident Evil 0 are also excellent.
Zelda: Twilight Princess is also massive, Windwaker less so but still pretty big.