Barely? WTF are you talking about? The PS2 has no problem with my gta games so I think your system is screwy. Hell, GTA barely pushes the limits on the PS2 compared to some other games.
I really hope that Rockstar improves on the graphics. That and a different storyline with new twists and turns would truly be great. We can all trust in Rockstar though. I'm sure they'll come through.