when you play oblivion, if you have a good machine I recommend getting some good mods for it.
as far as other games, well, stalker shadow of chernobyl is a nice grungy fps/survivor game
havent' played fallout 3 but the first 2 were classic so it's worth looking into
battleforge is an interesting rts/ccg mix. you can play for free enough to figure out if you like it but eventually to really advance you'll have to spend money on more cards.
mount & blade is kind of a first person, real time rpg... except the actual combat has as much to do with aim and timing the swing of your weapon as with a numerical skill with that weapon vs. the numbers of their armor etc. although in the beginning you can kill/knock unconscious pretty much anything if you hit it when you do 'couched damage' with a couched polearm on while riding fast on a horse, which you aim by steering the horse...
plus, it also handles throwing axes, knives, spears, and firing crossbows and bows, all on foot or from horseback, and blocking with shield, weapons, and unarmed, very intuitively. it's a very low key indy game, although successful. so you'll need to check out the mods, they make a big difference.
and that one ^ is the most fun I've had in a real time first person combat game. a huge running melee through a swirling crowd of mongolian horse archers, trying to nail them down with a jousting lance while arrows and spears whistle by and stick out of whatever they hit, decorating the bodies of fallen riders while their horses flee the field,..... is sexy