I wasn't born yet during the 2nd generation, but I do have a 2600 which I picked up out of curiosity in my 20s; even as someone who grew up in the 90s with the likes of SNES, Megadrive, PS1 and N64, the 2600 has an undeniable charm and simple pick-up-and-play elegance that I really like.

The likes of Space Invaders or Solaris remain awesome to this day.

Atari was the first console I played. That and a Vectrex but sorry that thing aged like shit. Important yes. Best? Not even close. It's just too primitive now. The best games on PC Engine and Neo Geo have aged wonderfully. Atari? 99% of it aged badly, even the good ones. 

Yeah, I think most folk don't understand how big 2600 was, and I think it really comes down to their first console being something that is, at best, as old as NES.

That said, from this POV, playing games on 2600 is really rough - I tend to play them from time to time, but honestly, they really show that early stages of game design mentality, and most arcade ports are just simply better played elsewhere.

Still, if by best we go with best for their time and impact on console industry, then yeah, I can't really go with anything but 2600.

By that standard, whatever was the most recent console not by the big four is the only possible option here. The tech has gotten better, the software design has gotten better. So there's nothing to even discuss here if what we're talking about is which system holds up best today. 

I'd argue that the 2600 generally holds up well as the games aren't complicated enough to have a lot of the problems common to say 3rd gen games, they're mostly very simple to pick up and enjoy.

For me, the biggest problem with the 2600 is that there just weren't that many fun games on the console, even at the time. I never wanted one despite immediately being drawn into video games forever with arcade games like Pac-Man. I could enjoy playing Combat and Space Invaders for an hour or so at my friend's house, but we found ourselves right back in the arcades popping in quarters and being fully engaged by comparison.

There will always be more mediocre games than good-to-great games in a system's full library, but the 2600 was by far worse in that regard than any other game console that ever matched its success. It certainly made its mark on the industry, but it also crashed the US home market with a multitude of terrible games that had no identity, originality or engaging gameplay whatsoever. And even its best standouts like Pitfall have aged pretty poorly compared to classics on the NES a generation later. I still respect the 2600, but it's definitely not the "best" console per this thread's criteria in my humble opinion.

Yeah esp as Atari's sea of shit is what drove Nintendo to create the Seal of Quality, so only licensed games were released for it. 2600 was getting porn games and stuff from Purina Dog Chow, eating up shelf space in stores. In stores, when game stores were not a thing. 

Yep.  I remember seeing 2600 cartridges for as little as a couple of bucks in bargain bins just to clear stock.

I always wondered what would have happened if Bushnell had managed to stay on after the sale to Warner.  Granted, Atari was on top of the world for a while, but that cliff due to all of the shovelware and the 5200 flop was devastating.

My friend's brother was a next level hardcore gamer beyond me and my friend and he had a Neo Geo Pocket Color that I thought was pretty cool. I think I played his copy of Sonic Pocket and Metal Slug on that for awhlie.

But my dad was a 60s and early 70s child so naturally got into the Atari 2600 and showed me his console with a few games, including that robot shooting game (Berzerk I think?) as well as Asteroids and I thought it was so cool. Got into that roughly around the same time as Mario/Duck Hunt on NES, my first gaming experiences ever.

PC Engine/Turbo Grafx-16 also since the PC Engine SuperGrafx failed miserably and they never made another console it's the best console that only really had one console.