Sonic Mega Collection+ because I think it might be the last time Sega released an unaltered port of Sonic 3 with the original music. That soundtrack slaps so hard!
Sheesh there's just way too many to narrow it down to my "favorite" so I'll try to give two interesting answers rather than just listing all the ones I enjoyed most.
Way of the Samurai is the PS2 game I'd like to see remade most out of all the games that haven't been remade already. It was jank but the combat had a lot of hidden depth, and the story could be changed by so many small compounding choices. It has insane replay value. Also the soundtrack is fucking great. Same composer as Tenchu and it shows. I've been whistling "Brutal Heart" and Tamagawa's theme to myself for years.
The PS2 version of Star Wars: The Force Unleashed I think is baffling better than its PS3 counterpart you're meant to like more. It has a lot more content than you'd expect for an inferior version made for a dying console, they absolutely did not phone it in. The PS3 version I think has a more cohesive story with a lot more fluff trimmed though and it feels more like an original modern Star Wars entry whereas the PS2 version feels like its firmly stuck in the discarded extended universe where all the non-canon stories die
The new gen force unleashed is pretty awful and I feel like I'm being gaslit when people said it was good. Clunky, buggy unfinished mess. Ps2 and wii version have more content and story and play better.
I also feel crazy when people dislike force unleashed 2 which is actually fun to play if short