Q*Bert's Qubes did what so many sequels have tried to do and failed; provide an improved and unique experience for the player in comparison to the original. Q*Bert may be vulgar. He may even look like the squeezy part of a turkey baster with legs. But he's also one of the most memorable game characters of the time and starred in one heackuva game here.
Pitfall II: Lost Caverns (Atari 2600)