FPS
STALKER, since you love you some RPGs. Unreal Tournament 2004 without a doubt is the best multiplayer FPS out there. Well, if you like them unrealistic. Half-Life 2, of course.
RPGs
Go old. Fallout 1 and 2, Baldur's Gate 1 and 2 (There's actually a mod out for 2 that reincorporates Baldur's Gate 1 so you can play BG1 with the classes, abilities, and spells from BG2. Tutu), Vampire: the Masquerade - Bloodlines (Fair warning, you'll need fan patches. Troika wasn't very good at limiting bugs), Neverwinter Nights 1 and 2, Planescape and Icewind Dale have always been recommended though I'll admit I never played both through, and Space Rangers 2 can be considered an RPG. It has stats and equipment, just a lot of other shit thrown in as well.
As for not being into RTSes, give Starcraft, Medieval 2: Total War or Rome: Total War, and Dawn of War a try. They're some of the best RTSes out there. But if the real time aspect isn't your thing, try out Civilization 3/4 (4's more user friendly and, in my opinion, better, but a lot of people swear by 3) and Galactic Civilizations 2. Also, lots of good things heard about Masters of Orion.
Also, is your lack of desire to play horror a lack of interest in being scared or because horror games aren't all that scary to you? If it's the latter, Call of Cthulhu: Dark Corners of the Earth is a really freaking scary game and relies less on body horror and hordes and a lot more on powerlessness in a hopeless situation. And some really freaking awesome chase scenes. And insanity. Well, and there's body horror.