I've been playing SNES games on my netbook, which is perfect for emulation of that and older systems. I haven't ever tried any NES emulators for some reason, but I will soon.

My favorites (that I can remember off hand) were Crystalis, Zelda, Metroid, Blaster Master, Mario Bros, Gradius, and Contra. I played the original Final Fantasy as well, which was (IMO) awful. Fortunately, not everyone shared my opinion, and amazingly it kept Square from going out of business.