I just made a post about this game! It was the first game I ever beat as a kid. Lots of memories with it. :]

I know I'm being lazy not checking on what I wrote months ago when this was first posted, but the Hidden Exit thing is something I wish Nintendo would make more use of in Mario games.  Honestly I would *ALMOST* say that SMB3 was better, if only for having more suits, interesting level and over-world design, and just the over all game.... but a fully-integrated overworld with replayable levels and rewards for exploring each (red)level is just awesome.

Seriously.  Like I mentioned a while back in another thread, one of my issues with Galaxy is that it frequently put the user in a situation where they had no choice but to take the path right in front of them.  But most levels in Mario 64 were set up so that even when you selected a different star, you were almost always able to explore the full level at your leisure, get a totally different star than the one you selected, or even collect 100 coins for a secret star, and I liked that freedom a little more I think.

New Super Mario Brothers integrated the idea a little bit, but not by much(plus I just....didn't quite like the game for some reason).  I'd definately like to see more of it though.