I have a similar story ... hours upon hours of THPS2 or 3 .. whatever was on GC. I unlocked every skater except for the last one, and had collected every point and board and medal available. Unfortunately I was using a third party memory card which then promptly became corrupted and all my data was lost.
(also lost all other game saves, and it was a 1024 card so there was a LOT on there)
I never really recovered. I still have that card but I only use it as a backup for my other GC card... all pointless really, now that I have a wii. But I just couldn't bring myself to play THPS for any significant time period again after that.