You can't make the game look better, unless it supports HD or Progressive Scan. The games graphics can't really look any better no matter what TV you have it on. Just the overall quality and display can be different with HD and Progressive Scan.
There is a way to make it "look better" but it's not going to be cheap: http://www.anchorbaytech.com/products/systems/vp20.php
One question, are you using the component cable, if you still using the standard cable, upgrade to component, the differance is amazing. can even play US version of GT4 in 1080i yes a PS2 can do 1080i
DBM_Bones is right, make the upgrade to component video cables, you will thank yourself for doing so. Pick up an optical cable too if your surround sound receiver (if you have a surround sound receiver)has it so that you can experience true surround sound. Ced