If you're not one of those people who likes to be spoonfed into linearity, and who wants to combine all the genres you mentioned (WWII, FPS, RTS) then you might want to consider Hidden & Dangerous 2.
It doesn't have all of CoD's enormous production values, but it also requires a higher degree of patience, has a slightly firmer basis in realistic combat, is less scripted, is a fair amount longer, with less linear missions, and often with multiple methods of completing your goals.
You might want to try the original (recently made freeware) H&D before you go ahead, though. While the controls and movement are pretty crap, it does show the "feel" that the sequel also has (i.e. sneaking and picking away at distant foes until in a tactically advantageous position from where to launch a fast brutal attack). The sequel's controls and movement is more like that a standard FPS (with the mousewheel being used to determine speed). The game is otherwise much more refined, prettier (uses an updated verion of Mafia's engine), and streamlined without being dumbed-down. It was rushed out a bit early, and does have a few bugs that need ironing out, even after the latest intitial patch, but a new patch is underway.
Some neat merits are the relatively freeform way of accomplishing your objectives (sneaking in surrendered enemy's uniform + stabby stabby + silenced firearms? Covering fire with machineguns and bolt-action rifles + fast assaulting SMG gunners? Lay explosives on fueldump as a distraction?), and the way the enemy AI acts (will often surrender if wounded, surprised, having their helmet shot off, outgunned, or terrified. Usually if at a disadvantage they try to sneak away and flank your position.), and the small touches like the (apparently) soon compulsory ragdoll physics, bullets passing through lighter obstacles, and ricocheting across harder surfaces (empty a magazine into a long concrete corridor and it is likely that many of the non-perpendicular wall impacts let the projectiles countinue hurtling along the wall).
H&D2 = H&D 1 + Mafia + Rainbow Six/Ghost Recon
If you liked the original Homeworld, then Homeworld 2 is more of the perfectly enjoyable same. A bit more refined, even prettier, with some missions a whole lot harder than necessary, as well as (in my opinion) a more rushed and less interesting storyline.
Gothic 2 is a good large freeform Morrowind-esque RPG.
Errr. haven't actually had time to play any other games since last Spring other than the above mentioned ones and Vice City.
[This message has been edited by Daeron the Nerfherder (edited December 10, 2003).]
If it breaks, you get to keep both pieces.