GT4 on the PS2 supports 480i and 1080i. you have to buy the PS2 component cables. after hooking up the component cables, you can select 1080i from the in game options menu.
there is one caveat though. it only supports 1080i in races. Game menus are 480i. So, there is lots of switching back and forth. very annoying, depending on the tv (some handle it better than others).