Super Mario Brothers 3
Sonic the Hedgehog 2
Completely agree. I'm not sure if any 'classic style' Mario game since SMB3 has quite been as good as it. SMW was okay, but somewhat overcooked IMO, like they were trying just a little bit too hard to make it bigger and better than SMB3, but just ended up making it feel bloated.

Sonic 2 took everything that was brilliant about the first one and refined it. "Chemical Zone" is just a stunning example of level design.
