Gotta be from Midnight Club 2 and 3 although World Racing 2 was good. Tony Hawks games have some good songs on.
Mine is that of Silent Hill 1. Although I find groovy those of even older games such as Wolverine and BattleToads
Suikoden II would be my fave! I've always loved those instrumentals, it perfectly blends with the gameplay and of course with your imagination.
I would have to say my favorite is Bioshock or Oblivion. I downloaded the Bioshock tracks and they are soooo good. Amazing classical music for a video game!
I totally love the We Love Katamari soundtrack. Some of the best dish washing music I've ever heard I also really like the Jaki Crush soundtrack (old SNES pinball game)... I even went to the trouble of ripping the audio from the rom and converting it to MP3
My favorite will be Final Fantasy IX and Final Fantasy X. I played Final Fantasy IX my self so the tracks was good. Final Fantasy X - Suteki Da Ne was really touching.
Tony Hawks 1 and 2 for me, Crystalis (NES) Shatterhand (NES) Startropics (NES) Dark Cloud (PS2) Final Fantasy 8,10 Super Mario World (SNES) Super Mario Bros 3 (SNES version in All Stars)... GTA San Andreas (great soundtrack)