Playing
half a dozen other
3d platformers has really
shed new light for me on what makes Super Mario
64 great, for a couple of reasons. One is that it really does take practice to become good at managing both the character and the
camera at the same time. Another is that none of the other games have anywhere near the same
noise-floor of fun as Super Mario.
It's the control.
In "other" 3d platformers, you can move around and you can jump. And that's about it. There are other moves, but they're usually gimmicky, like shooting eggs, sprouting bird legs, or pulling out your coconut cannon or frying pan.
Mario performs acrobatics. Different kinds of jumps. He bounces off of walls. The variety of moves that exist mostly for their own sake is impressive, and so is the attention to detail... for instance, the different animations for different movement speeds, and for stopping at different speeds. The different idle-animations for different situations. The stars that appear when you hit a wall headfirst.
Once you've got control of the character, just moving around in this 3d world is fun. Add goals to the mix and you've got a powerful game experience. It's a fantastic feeling when the moves you've been performing throughout the game, just because they're fun to do, actually become useful on later levels.
But it always comes back to frolicking about the castle grounds. Running around is fun. Just like in real life.