Cross-X on 15 April 2010
Assassin's Creed II is the most improved because AC 1 was quite bad and AC II fixed a lot of the problems and that's what made AC II really shine out.
IMO not so much Bad Company because though Online is far better in Bad Company 2 than 1 but both games have crap single player campaigns.
Uncharted and Mass Effect were both great new IPs to start out and both sequels are Highly Acclaimed Titles so they are improved sequels, but they did not jump from "mediocre game to outstanding impressive game" like AC II did.
COD4 to MW2 went backwards so I don't see why that's even an option.
