Well, N64 "emulation" is more N64 approximation right now. The majority of the library doesn't run correctly. There are maybe 10 games that work really well, and the rest range from not working or working with noticeable bugs. So you have to try the games out on 3 different emulators and try different plugins to see if you can get things right. Surreal64 on modded Xbox actually includes Project64, 1964, and UltraHLE to choose from and it still won't run anywhere close to all of the games.
I haven't used Nintendo's Virtual Console on Wii yet, but it seems to do the job well. Apparently it just uses the ROMs from the carts with various tweaks. I'm sure it's HLE. I'm just not that interested in buying the games again.
PJ64 runs Mario 64, both Zelda's, Mario Kart 64 and F-Zero X.
That'll do for me