I tried a 3D Pacman once. It just wasn't the same... 2D rocks! >_
Somehow, Mario with a pair of blades and an UZI, fighting ninja style through level after level, decapacitating opponents just doesn't add up. It would be Mario in name only!
For some of those oldies, the stylised gfx were an integral part of them. Especially the fast and furious ones, you need effects that makes it clear and unambigous what is happening on screen, something you can't always do adding more polygons and colours (and a third dimension).
Others could probably benefit from a "re-make", although I would settle for a bunch of oldies that would actually just run on my computer without resorting to emulators.
Hmm... Forbidden Forest running on that Crysis engine on the other hand... *drool*