this is very tough. so many consoles are good for so many reasons.
NES gets a nostalgia pop, and props for kicking off the mainstream video game culture.
if i could go back in time, i would convince my younger self to get an SNES instead of Genesis. My brother and I still got a ton of use out of the SEGA, but Sonic and Altered Beast aren't enough to make up for a lack of Mario kart, Starfox, Final Fantasy and Chrono Trigger. Not to mention, 6-button controller > 3-button.
As amazing as PlayStation was, it still had limitations (long load times, major slowdown with multiplayer games, 2 controller ports). But if I had to pick just one from that generation, it would be PS. N64 provided a lot of good times with groups of friends in Mario Party, Smash Bros. and Goldeneye, but its offering of single player games was pretty shit.
I would take XBox over PS2. The controller was better, the system was easier to mod, and the graphics were better. neither system had any exclusives that sway me either way. Gran Turismo is boring, and Halo games suck my balls.
I'm not familiar enough with the current gen to have an opinion, other than i think the Wii is shit. But that's more due my preference in games than any specific shortcomings of the system.
so for ME, super best ever console is XBOX, I guess? I fully expected to declare PS as my #1 when I started this post, but upon reflection, I have to take the box. bringing console games to the internet, putting in a dedicated hard drive, 4 controller ports, XBOX is the system that the competition tried to emulate in this current gen. My opinion may also be slightly biased, because the XBOX that I mainly used was modded and augmented with a 150 GB hard drive. But I have a shitload of great gaming memories from that system, including single-, 2- and 4-player games. most of my great gaming memories from PS are single player games, and all of my great gaming memories from N64 are 4-player games.
XBOX did it all, and did it best (up to that point)