Any type But I don't like puzzle games
Most of these aren't hidden gems, but are great fun anyway:
RPG:
Baldur's Gate: Dark Alliance
Racing:
Need for Speed: Most Wanted
Burnout: Revenge
Shooter:
Metal Gear Solid 3: Snake Eater
Serious Sam: The Next Encounter
Destroy all Humans!
Ratchet & Clank
Black
Fighting:
Mortal Kombat Deception
Tekken Tag Tournament
Skating:
Tony Hawks Underground 1 and 2
Horror:
Silent Hill 2 / 3
Stealth:
Metal Gear Solid 2: Sons of Liberty
Sly Cooper
Sim/Management:
Theme Park World
That's a few to start with :)