Finally, I agree with Clam, I do enjoy playing Mario games. Sure, they're not original, but they're a whole lot of fun, with some pretty decent setpieces.
They are probably the most original games out there.
Sure the basics of the game is run/jump/etc .. But there will always be something new and original around every corner to keep you playing.. You'll always be suprised by something.
Unlike something like halo, where you know you're just running down corridors for the whole game, moving a pointer around and pressing X when it's over an alien.