I think the PS2 graphics chip had an immense fill-rate, not rivaled even by current graphics chips (I could be wrong, but this is what I remember).
Also, rating GPUs based on their pixel fill rate stopped making sense around a decade ago.
Granted that was years ago, so I might be mistaken. But it's still a lot of speed for a device that was made more than 13 years ago...
No wonder the first PS3 came with the Synthesizer chip built-in, rather than emulate it.