Any of the Donkey Kong Country games would probably yield some good discussions about how well they've held up over the years. Personally, I'd like to try the second one, as I've never played it (and I hear it's the best of the trilogy) but I'd be willing to be the first one would be more popular.
Mystical Ninja has some true believers, although I think the N64 one is generally considered far superior to the SNES one. I don't know much about the series but I'd be willing to give it a shot.
ActRaiser would be a great choice, since it's such a unique game. However, considering the RFN crew has already discussed the game before (or was that Retronauts? I forget) it might be out of the running.
I'm sure someone's going to mention Mario RPG, so it might as well be me. I played it for the first time when it came out on VC last year. It wasn't a bad game, but compared to the Paper Mario and Mario & Luigi games it pales in comparison. Plus, I'm hoping that the original Paper Mario game will win the upcoming N64 poll, and I wouldn't want to see both games win the polls so close together.