Oblivion comes to my mind first. It still looks decent, but when looking at it, it's hard to not realize how much has improved since - and we're talking about a game that looked absolutely gorgeous back then.
I think I might also have to say Metal Gear Solid. For a PS1 game, it still looks absolutely stunning, but it does look kind of dated. In a way, I think it looks dated in a way different from Oblivion though, which is why I also hesitate mentioning it here. On the other hand, it's remarkable how well the other home console games in the series have held up.
RE4 looked amazing in 2005, to the point that I and my school-friends didn't see what the fuss was when the 360 launched later that year. Even when I first played the game in 2009 it blew my mind how good it looked. But going back today the textures are absolutely terrible, through the models and lighting still hold up. Same with God of War. Other than the large bosses it looks bad, but it also made the 360 look unnecessary at the time.
Sonic Adventure. It was so far ahead of everything else graphically at the time. But the models aged very quickly once the PS2 launched.
FF7. The FMV's and pre-rendered backgrounds stopped hiding how terrible the polygonal models were very quickly.
Star Fox. A milestone in 3d graphics on a console, but it aged like crap.
Not counting games like Metroid Prime, Rogue Leader, Gears of War, or Crysis which still hold up well.
World class leaderboard golf - this one didn't wow me with graphic, but with sound. It had real sound effects including speech which sounded good enough, created not with a sound card but with a pc-speaker. I experimented with pc-speaker before, all you can do is setting the membrane outside or inside. No volume, no waveforms, nothing. But still this game managed great sound. Impressive!
The first Dune-game had dream-sequences. They started off by the screen content getting wobbly. This used the CRT-screens of the time. An electron ray illuminated one pixel, then magnets moved the ray to the next pixel and intensity was changed. So one pixel after another the image was constructed. At the end of the line, the ray was moved to the beginning of the next line. At that point the game changed the starting position for the new line and this for every line and different for each image. That created the wobbly image. That is actually not possible this way with modern digital monitors.