Thank you for all the suggestions.
I never heard of Oblivion but it looks very good.
For fps, I have UT, UT2003, UT2004, and Halo. My favorite (single player) by far is still the original UT "1999" with the OSX patch (playing CTF matches). I was looking at Crysis and was wondering how it compared to the others as far as game play. Would you recommend HL2 out of all the fps games ?
I was also considering Heroes V or Fallout 3. What is your opinion of these titles ?
After Marathon

, UT has to be the best multiplayer game I've ever played. I spent many years going to Lan parties to duke it out. I never did any Crysis multiplayer, but my impression is that it is not nearly as robust as UT is with game varients, plus Crysis is a resource hog. Maybe someone who has played Crysis MP will comment.
As stated in my previous post HL2 is highly reccommended!

I think the original HL and HL2 represent the greatest solo adventure shooter game ever created. The graphics are not as refined as Crysis, but it's gameplay is more enjoyable IMO. But Crysis is a different sort of shooter with it's sneak factor. You wear a suit with a stealth mode that makes you invisible for short periods of time before it has to recharge. I love the jungle island environment (like Far Cry) where you can spend
a lot of time sneaking through the weeds to avoid detection.
I never played Heroes V, maybe I should look at that? I was disappointed in Fallout 3 mostly because I did not care for the post-apocalyptic environment. It's by the same company that did Oblivion (Bethesda Software) so the mechanics are similiar, but Oblivion is a much more pleasant environment to explore. I think a post-apocalyptic environment could be fun, but F3 seemed very drab and dreary to me.
Some things about Oblivion:
There is a main quest chain, but if you ignore it there is no adverse result. It just sits there until you do it. There is even a mod (for the PC version) that gets rid of the main quest! Once you start there will be this pressure to save the realm. My recommendation is to do it, but you can do it at your pace. In other words, you don't have to ignore every other quest to get the main quest done. BTW the PC version has tons of mods. I don't know about the Xbox version.
There are a huge number of dungeons, but they all have a similar feel and look. They are either caves, forts, or Ayleid Ruins. And the controversy with Oblivion was that combat scales with the player skill level. The advantage of this is that you can explore any dungeon at any skill level and face a challenge. The bad thing is that unlike a game like WoW, you can't really get in over your head unless, you level the wrong way. For more info please see the
MacRumors Oblivion Tips and Cheats Guide which I put together. See No.13 "Leveling the Right Way". Some players say scaling combat makes it feel repetitive. But lets be honest, what game does not have repetitive Player-Versus-Environment combat?
Oh, did you ever play Bioshock? I forgot to mention that- outstanding RPG! Dark and threatening, great enviroment! I started playing it on the Xbox but switched to the PC because there are some combat issues that I could address with my Norstomo N52 (controller) on my PC, that I could not handle with the Xbox controller. Issues like being able to rapidly switch active abilities so when a Big Daddy hurled something at me, I could switch my psi ability, catch it (using the force)

and then hurl it back at him. With the Xbox, I'd have to pause the action, switch my active ability, then restart the action and hope to catch the item tossed at me. BTW, catching stuff was not a requirement, but since I had the ability I wanted to use it. A Bid Daddy barreling down on you really gets your attention. If they catch you, they pound you to smithereens in a couple of seconds.