I saw this post mentioning the Xploder HDTV PS2 Upgrade. Supposedly, this will allow you to play your PS2 games in Enhanced Definition (480p), HD (720p or 1080i) or VGA. I am not sure this will work. The post mentions that it is a device, and comes with component cables. Also it sounds like there is some software that needs to be installed on the PS2. This makes it seem that this will connect to the expansion port of the PS2 (This implies that it will only work with the original PS2), and that there are component cables and a VGA port on the back.
I don't imagine that this will work that well. The PS2 and the games written for it can only output up to 480p. So essentially this is is just a line doubler. And I don't think that the quality of this line doubler would be better than the line doubler built into most HDTVs.