The NES was the first one that I had, but the N64 was my favorite. All the games were amazing, the controller was awesome and comfortable. The multi player experience, albeit only split screen was the most fun that you could have with friends. Some games were really both impressive and fun, like Goldeneye, one of the best games ever. Super Mario 64 was amazing too, it was the whole 3D thing done right for the first time. Wave race 64 was the best thing in the history of mankind.
The Wii is a close second, I am still waiting for something as fun as the simple Wii Tennis game, and nope, that kinect is not the same, that thing doesn't work at all.