Best - Thief 2, System Shock 2 To a lesser extent the Max Payne and Hitman series got better which each sequel, until the Max Payne 3 and Hitman Absolution that is. Worst has to be Deus Ex Invisible War as other posters have mentioned, I think if you were to conduct poll it was definitely be first on the list of worst sequels ever. In more recent years most game sequels seem to be fairly disappointing. Not bad games in their own right, just failing to live up the predecessor(s). I'd include Doom 3, Half-Life 2, BioShock (I'm counting it as spiritual successor to SS2) , Deus Ex Human Revolution, and Thief 3 in that list off the top of my head.