GTA3 is notorious for this. You'll find a few posts from me and others on this subject. I have concluded that it is badly pressed. You'd have to take it to your local Trading Standards Office in order to have it checked against the ECMA requirement for DVD-R. Or you can download the NERO benchmark program and via a DVD-ROM on your PC put the DVD through its paces. In fact I think I'll do that.

The situation was eased as follows:

1 I cleaned the lens - that got rid of the read error
2 I had the laser recalibrated - that made loading faster
3 I switched to a different PS2 - problem appears to have gone away with that calibration