I dont really know what an emulator is, if you're talking about memory then get the Expansion pack. As far as games go get.....

Goldeneye (its a must)

Mortal Kombat 4

WWF No Mercy

Those are the best three that I can think of right now.

The best emulator that I know of is Project64.

http://www.pj64-emu.com/

If you want to get better graphics on certain games then you have to use high-res texture packs. http://www.emutalk.net/forumdisplay.php?f=110