Should you buy Fallout Three or assassins Creed Two

That's like saying, 'Should I buy a dog or an elephant?'. Fallout 3 is an FPS/RPG whereas AC2 is a third person Action/Adventure game. Fallout definatley has more replay value. AC2 is about a 20 hour piece then a dust collecter. Fallout is much more open and AC2 is more mission based.

In short, Fallout 3 is like Mass Effect or Dragon Age Origins, (2 Bioware RPG coincidently)
And Asassins Creed 2 is like GTAIV. The game is basically climbing buildings and such. AC2, fun, but Fallout 3 is more bang for your buck.