Oh, boy. That's a lot. I often buy games I have no idea of what they are, just because I need something new to play, and they're cheap, and some of them are true gems. Gothic 3 for example, I'd heard so much about it before, and (since I disagree with most people about newer games) I didn't think it'd live up to that. In fact, I thought it'd be awful. It wasn't though. Penumbra is another game I got at the same time, which I didn't know anything about, and it was awesome. Truly terrifying. (Until you get to the place with dogs everywhere it you just go "meh".) Genesis too, which I expected would be fun for a few hours playing skirmishes but had a really deep and involving story. Much more so than I expected at least, and you got to choose your responses, something I don't think I've ever seen in an rts, not that it affected much, just a little. The gameplay is quite fun too.
Oh... I'm rambling... Oh, well have fun reading this.
Mount and blade is another game like that, I saw it mentioned somewhere and tried the demo. Great game, so I purchased it. The thing about it though is that it's always improving. The difference between how it is now and how it was when I got it is like the difference between the first GTA and the last one. Except that Mount and Blade was awesome when it was like the first GTA and that it now is one of the best games out there. Lugaru too I got the same way, it seemed like it would be fun for five minutes, but it was much deeper than I thought, and the satisfaction every time you stab someone with a sword, kick them, watch them fall 200 feet and hear every bone crunch when they hit the ground is amazing. That your sword will drip blood as you walk towards your next foe is a nice detail as well, and that you can throw that enemy into a wall so hard you see the cracks on the wall...
Bloodlines must go here as well, I think. I expected it to be reall good, but when I actually played it through for the second time I realised just how much I'd missed. That game is truly a gem.