I also still like some Atari VCS games with a few still being playable today like 'Hero'

 Yeah, gamecube games look quite nice if they are rendered at 1080p.

It really depends. I find it hard to go back to seventh generation games, because 7th gen really just looks like bad 8th gen. 6th gen games have their own 'style,' and sometimes there is a particular charm to it. I'm most familiar with the PS2 from the sixth gen, but there is a definite 'style' to the muddy textures and foggy backgrounds. Obviously, it worked best for games like Silent Hill, but I also think it gave a certain weight to the original Persona 4 that was lost in the brighter and sharper Persona 4: Golden.

Going back further, I think the N64 almost always looks gross whereas a few PS1 games (like the Spyros or Xenogears of FF9) hold up. I like the look of most SNES games, but Batman: The Video Game and Battletoads are the only decent looking NES games.

Sprites - 16 bit
Polygons - PS3 level

I'd play with an ugly potato if it's fun.

I'm fine with anything really. I still play Streets of Simcity from like 1998 with its awful graphics every now and then, just adds to the charm for me. It's a game to game thing, rather than the entire system itself.

Ahh... Good ol' Combat on the Atari 2600.

It played well. Until they bought in camo tanks which you can only see when you shoot. Epic local multiplayer though.

NES. I can't play Atari even tho first games I played was Atari. NES is as far back as I can go.

For a game today? 7th gen level 720p with high res textures and 30fps is the lowest I'd EVER want to go now, with the exceptions of a few low res textures here and there and maybe some simple geometry for backgrounds. If indie studios can produce stuff like this, and fan made games and film can wow us, no excuse for people who get paid a professional salary shouldn't be able to.

The exception is art style. If it's MEANT to look like a childs story book, or a SNES game, I'm fine with it

As long as I can tell what to do, I don't care how good the graphics are. I'm fine with 2nd gen and very early 3D graphics.