Crimson Skies
Doom 3
Elder Scrolls III: Morrowind
Fable
Lord of the Rings: The Return of the King
Mechassault
Sega GT/Jet Set Radio Future
Splinter Cell
Return to Castle Wolfenstein
Star Wars: Knights of the Old Republic
Star Wars: Republic Commando
Ultimate Spider-man
X-Men Legends I & II

I don't know what I'd recommend to you personally, but I bolded my favorites.

I never finished Doom 3 or Mechassault though they didn't seem that bad. The Sega GT/Jet Set games came with the Xbox, so I played them only a little before I got my own copy of Halo CE and said farewell. I haven't actually played Republic Commando yet, but it has been recommended to me over and over.

Morrowind and Knights of the Old Republic are some of my favorite RPGs of all time. Neither of their combat systems are that amazing, but they presented fascinating and immersive worlds (and characters in the case of KotOR).

Return of the King is a button-smasher action game. It's... okay, but its predecessor, Two Towers, which I have on PS2, did its job much more effectively.

Return to the Castle Wolfenstein might be a terrible game - I don't know. It was my first online game so I have a bazillion memories with it. Since the servers are shut down, I guess there's no point in recommending it.

Crimson Skies is a fun dogfight game in the style of The Rocketeer (Diesel-Punk). For some reason, that's what I feel I should recommend to you, but I can't tell you exactly why and I might be completely wrong.

I might recommend the Spider-man and X-Men games if you grew up on their comics and cartoons; they are some of the better comic-to-game adaptions, if a bit simple. Fable was also a great-but-flawed game, with memorable music, style, and voice-acting, and it's probably the closest I'll get to a Discworld game.