GC very rarely used AA. I'm not sure I've ever seen it do AA, actually. It has some nasty drawbacks when used on that hardware. Really hurts performance.
I've heard it did in the first Splinter Cell. Maybe they're not actually using FSAA, but the games sure look a lot smoother than their PS2 counterparts. For example, bad guys in Spartan: Total Warrior don't flicker and jag in the distance the way they things often do in PS2 games, even though you can sometimes spot an edge that shows aliasing. It might just be the deflicker filter, which I don't think works for 480p images.