I say Tomb Raider. I enjoy the supersmooth animations of Lara Croft until this very day. It was pure magic back then.

Honorable mention to Ocarina of Time. The environments blew me away as a kid. But Link didn't move as smooth as Lara did. =P

While much more rudimentary than other games, I always thought 1080 Snowboarding looked fantastic! Especially the animations of the way the snowboarders would move while in the air or even fall.

Late generation N64 games like Perfect Dark and Conker. And Animal Crossing looks so good that people really believe the series started on the GameCube I guess. And games like Star Fox, Rogue Squadron and F-Zero are very impressive by how good they look and perform.

Great post. 

Burning Rangers is up there for me too, the dynamic coloured lighting and extensive use of transparencies was crazy impressive.

I'd actually never seen Omega Boost before, and it does indeed look phenomenal, great use of particles in particular, thanks for the heads up.

If I had to narrow it down to just one game, it'd probably be Conker's Bad Fur Day. It could almost pass for a low level Dreamcast game with the amount of detail is pushes. It has realtime reflections, dynamic shadows, coloured lighting, Conker even has individually articulated fingers in a gen where like 99% of characters had blocks for hands.

Honourable mentions would go to Legacy of Kain Soul Reaver for its large, complex, and visually stable levels and higher resolution than most PS1 games, Ridge Racer Type 4 for its lighting and car models, and on the Saturn side of things Panzer Dragoon Zwei for its stunning modelling and worlds.

Ocarina of Time and Majora's Mask, hands down. They created vibrant, colorful 3D worlds for Link to explore. Nothing else came close.

The first Turok game was really jaw-dropping, coming from games like Doom and HeXen. Full 3D and fast-paced, well-animated enemies.

Wave Race and 1080 were also some of the most realistic graphics I'd seen at the time.

On the PS1, I wasn't impressed with most of its attempts at full 3D. Gran Turismo sticks out the most over there, but I felt that Square Enix's approach to Final Fantasy, combining 3D models and battle scenes with static pre-rendered backgrounds, was probably the best approach to take for the time. Final Fantasy VIII looked more impressive than most Dreamcast games, and the Dreamcast released the day before in the U.S. The battle scenes were especially well done, even setting aside the summons. I really wish Nintendo had been able to finish Mother 3 N64. That game looked pretty promising.