Early on it was mostly arcade games that blew me away, they were always SO far ahead of anything you could get at home...
Glorious 60 fps, 480p with some insane AA and graphics that were easily a generation ahead of anything on my home consoles
virtua fighter, daytona usa, rage racer, some sega f1 game I can't remember, rush, sega rally etc were all mind blowing, this continued all the way till the ps2 era
I remember seeing some skiing game at an arcade during the psx era that looked vastly much better than anything that came out on the ps2 years later, can't remember the name though
battletoads on NES, because it was my first coop experience, I've wanted more coop ever since
sega rally on the dreamcast also blew me away when I first saw it in a store, that same 60 fps from arcades and way better image quality and textures than psx games with the shiny smooth looking car , it was like arcade quality graphics and smoothness at home
cs on pc in an internet cafe, I think it was the first game where I saw mip mapping being used, something simple as basic texture filtering made such a big difference, and the image quality was so good on the pcs (while I was still stuck with a psx at home and an old 386-2X dos PC)
medal of honor on psx, not the graphics but the hilarious AI that threw themselves on grenades or kicked/threw them back at you
to see some basic interaction from the game AI like that was new to me
Quake 3 on pc, ROUND arches and curves you say? What is this wizardry! (funnily enough we haven't seen them in other engines since, lol)
the game looked so damn good overall
mgs2 demo on ps2, the boat, the rain, the bridge, the cloth , the particles, the interaction, the AI, the smoke from the fire extinguishers , the reflections, the breakable objects, the realtime shadows
just everything about it was just amazing
they really made good use of that small super high bandwidth ram pool of the ps2
it looked so far ahead of anything else on consoles
crysis on pc back in 2007 (and during e3 in 2006), it was just insane... literally 4 years ahead of anything else
dead or alive 3 on xbox
the snow, the large levels, the character models, the reflections
holy shit that game looked good
I think overall the arcades were the most impressive for their time though