Keep in mind that many widescreen PS2 games don't send the signal that auto-triggers widescreen mode in TV's.
For instance, I have to force my TV into "16:9 enhanced mode" for the PS2 version of SSX3 and Ratchet & Clank 3, whereas the Xbox almost always automatically kicks that mode in once I set it 16:9 in the console's menu.
Finally, a lot of PS2 games only have the actual game itself in widescreen mode, not the in-game menus. SSX is like that.