Playstation has been doing this for a while now, releasing all their old games in HD goodness.
The problem with xbox is they dont really have any old games to revamp, it would be pointless to remake gears of war or something
If were talking about 3rd party games its a bit tricky as it all depends on the developer. Activision has proven with goldeneye that you cant rely purely on a sense of nostalgia to make a good game.
Saying that, i would love to see an updated version of all the old Resident Evil games.
Imagine a remake of the first 3 Resi games with updated HD graphics and a Dead Space control scheme, i would be in gaming heaven.