Symphony of the Night
For best 3D graphics, Einhander (or Tekken 3 if you can tolerate the interlacing).
Spyro 3 IMO. It just looks wonderful.
Can't say artistically but Delta Force Urban Warfare is the most impressive for me technically; that or the insane draw distance one, can't remember the name
The FMVs in FF9 looked pretty amazing for the time.
The rest of the game looked nice too, still does in my opinion.
Wipeout 3 is pretty awesome. Pictures alone don't do it justice.
Ridge Racer Type 4 is probably my number 1 visually, but it cheats a lot (I don't think I've ever gotten more than 3 cars on screen ever, including your own, on a track with 8). Still, it's extremely stylish, Namco in top form. Environments are extremely detailed, cars gleam with a decent reflection mapping implementation, and they look quite nice, good detail.
Wipeout 3 is a close second. The ship models are pretty lo-poly, but all of them can be on screen.
The environments are detailed and the game runs with high horizontal resolution (IIRC, it runs at 512x224 in NTSC).
Also has a ton of style to it.
Omega Boost is my third. Very, very impressive lighting effects at all points, nicely detailed models. Oozes with style, particularly due to the lighting. Gets quite a few objects on screen.
never liked how people looked up close in Vagrant Story, but it's a damn pretty game for the machine
it's got pretty nice lighting in particular
It's the only game series that could pass for PS2/PSP games.
MGS1. Just finished replaying it again and hot diggity damn.