Well, i'm fine with playing Atari 2600, and NES. I do have a hard time going back and playing most PS1 & PS2 era games, though.

SNES. Also Final Fantasy 8-9 still look great to me. Imo it's more to do with art than tech, but the tech can limit the expression of art.

Super Mario Bros on the nes is fine, hell Pokemon red on the Gameboy is fine. Anything below that there's a problem, atari 2600 for example.... I mean theres literally not detail, so little that the games have almost no personality.

All of them

I didn't realize Pong was a generation.

Gen 6. The dreamcast was the first console which made me think wow this looks amazing. Thats what i thought when i first played soulcalibur in 2000.

Realistic visuals 7th gen, cartoon 6th gen

I think I started gaming on the second gen but didn't own a console until the third. I can't bring myself to play an NES game but SNES titles are fine. I HATE PS1/N64 era graphics and most PS2/Gamecube era games look good but play badly.

Last gen still looks fantastic to me, though. That's why I'm cool with backwards compatibility. People say "Nobody cared about BC on the WiiU" but my argument is that the WiiU is BC with the Gamecube. A console nobody owned with games from a gen that hasn't aged well.

SNES-Genesis. Sprite based games are the ones that never age, due to having a very timeless style. NES and gens before are too primitive, and from PS1-N64, the first days of 3D haven't exactly aged that well.

Unconditionally, 7th gen. But even the 4th gen has a lot of games that are just fine. And I'd say the 5th gen is mostly OK too, so that may be where I would practically draw the line. But it depends, it's not individual gens that simply determine it.