I've seen a lot of mention of Tetris, and I concede that it is beyond criticism, but that probably owes to the lack of depth, rather than brilliant game design.
I also saw Heroes of Might and Magic 3, which I'm inclined to agree with also, that was a brilliant game that was only limited by your own playing style.
I'm going to add Banjo Kazooie to the list. It had charm, visual aesthetic, a good soundtrack, varied gameplay, a proper difficulty curve and my 2 favorite game heroes of all time. I've thought about this before and I can't find a fault in the game... 100% completion isn't required, but theres benefits to completing more and more of the game (unlocking red honeycomb, extra feathers/eggs etc.). Exploration of the overworld isn't required but its helpful (finding teleport cauldrons, cheato books etc)...
Fuck all this talk, I'm going to go play it again.