Cyraxpt: Warhammer Space Marine: It's a good action/hack and slash game and you really don't need to know much about the Warhammer universe, i borrowed it to a friend who never played a Warhammer game (he doesn't like rts) and he really enjoyed it and now he's a fan of that universe (still not wanting to play the rts, lol).
The Darkness 2 - I enjoyed it, it's not as good as the first but it does have a good gameplay and ok story. Tons of violence! :)
I'll keep an eye on Space Marine as well. You are right that I don't much care for RTSes, so I'll see with that :D.
Also, if the first Darkness is better, surely I should aim for that? I'm not too fond of horror games either, though...they seem to oscillate between jump scares (which just irritate me), and boring overdone blood-stained wall stuff. I played Amnesia for a bit before getting somewhat bored of it as well.
MarioFanaticXV: Really? I've only ever heard one person say V was better than IV, and they said they simply don't like strategy games. Civ IV vanillia is comparable in detail to Civ V Complete, while Civ V just felt very dumbed down after IV. The only improvement V made was the switch to hexes, but it was one step forward and a dozen steps back. Gods & Kings and Brave New World did some damage control, but even with them, it still feels kind of hollow.
Also, you shouldn't take Yahtzee's reviews seriously. Ever. He's a comedian, not a reviewer, they're not meant to be accurate representations of a game, that's not what he's going for at all.
As I said, I'm not REALLY one for RTSes. The fellow who said that had it something like Civ V with the expansions, Civ 2, Civ 3 and then Civ V without expansions.
I watch Yahtzee's stuff mostly for comedy, but his opinions very often do happen to match my own, which is why I follow them. Still, I'll keep an eye on Castlevania, since you say.
Nirth: After going through your steam list I have this recommendation:
Install the games your have and try them instead. You have 644 games on Steam alone and only 261 have been played at least 0.1 hours, barely 40 games played above 10 hours.
The list is a bit of a confuser in that regard :D. The vast majority of the games in my Steam list are Humble Bundle games I played without Steam, or free to play stuff that got added there, or games that I've played before I got them on Steam, or in the case of distastefully DRMed stuff, things I got annoyed with the DRM of, so I downloaded "elsewhere" and played it DRM-free (something I suppose I'd rather not do if I don't have to). Most things that I played for less than an hour or two is stuff that probably didn't stick to me, so I uninstalled them.
There is of course loads and loads of stuff I haven't tried and much that in fact I want to get to, possibly almost half of the remaining list (and that's not even counting the Dragon Age freebie and Humble Origin Bundle stuff I have on Origin but have never tried). But I'd still like to keep my eye out for good deals on good games I may not know about!
I've been recommended Dark Souls before, but I don't have a controller, and I'd prefer not having to get one...I like my PC gaming with the keyboard and mouse, even stuff like Darsiders and fighting games and such.
Also, I'm even more confused about Assassin's Creed than before :D. I had heard that Brotherhood was mostly multiplayer focused, and I'm the absolute exact opposite of multiplayer focused... I know lots of people prefer to go in sequence for the story and not to miss out stuff, but I like to think most games are self-contained units...so disregarding that as an issue (but certainly not overall story quality of the individual game)...what should I look out for? 2? Brotherhood? 3? 4? Black Flags? Not that it really matters, I guess, with the uplay stuff.