In terms of power and how many polygons that can be pushed, the N64 wins hands down, but does that mean the graphics are better? Full 3D games, the N64 beat the PSX, but what about 2D games? 2D games would look much better on the PSX than the N64. A lot of RPGs on the PSX were developed using prerendered 3D, so thanks to the large amount of disc space, could have great looking games despite not being able to handle those same graphics in real time. Resident Evil 2 is far from the best looking prerendered 3D game on the PSX and on the N64 port, the 3D models look better, but everything else looks worse.
These graphics might be prerendered, but they're also better looking than anything on the N64, so "technically' the PSX had better graphics.
And not just prerendered games, but straight up 2D which the N64 couldn't handle well.
Also, while the PSX can't do 3D as well as the N64 can, there are better textures in the 3D environments.
So, the way I see it, the N64 can only push better 3D, while the PSX can have better textures, better 2D, and also great looking prerenedered 3D since it's pretty much 2D, and don't forget the higher quality and larger amount of audio because of the extra space as well.
