Sequels that come to mind:

Toy Story 2 and 3 (both much more clever and funnier than the original);

Gremlins 2: The New Batch (on equal level as the original, except in much different ways);

Kung Fu Panda 2 (good but not great sequel to the underrated first film);

And Back to the Future Part II. I'm much more a Part II guy than a Part III guy; Part III is where the "look, it's the exact same actor, but it's his great-great-grandfather / mother!" schtick got really tiring. I get everyone's problems with Part II, but I think it's a good time. The original is much better, though.

Does Big Trouble in Little China count? Semi-sequel to Buckaroo Banzai? No? Okay...