The N64 takes a lot of shit, and rightfully so in many respects, but there are some great games on the system. Sure most games suffer from those early 3D game challenges like a camera that gets in the way, but plenty of games are still fun IMO. Last year I got hooked on Banjo Kazooie and it was a title I never played BITD so it wasn't the nostalgia effect. If you stick w/first party games you're in good shape and I remember some of the Star Wars games being fun as well.
Generally speaking, I don't fall into the nostalgia trap for the most part. Case in point, I got an Atari 5200 years ago, which I never played growing up, and really enjoyed a few of the games. Yes, the controllers are shit, but you can get adapters. Qix and Pole Position on that platform are still fun to me. The NES was the first system we had that I was old enough to really understand, so if there would be any nostalgia effect it would be there, but revisiting the NES library over the last 15 years I've realized how much shit there really is on that system.
I would have to say the Jag is the only system I wish I could quit. I keep getting drawn back in only to be disappointed nearly every time no matter how much I try to appreciate it for what it was back in its time.