I find that "The Gears" by Dethklok seems quite appropriate for any game you play a Clockwork Knight (or, to a lesser extent, a Rogue Scientist)
And I just go with DoD's in-game music. Then again, I'm the sort of person who prefers to listen to what games have to offer unless the music is truly atrocious (that, and it helps me with finding usable musical pieces for my group's GM).
There are very few games where I like the music enough that I don't get tired of it after a short time. And nearly all of them were Bethesda games. But even Fallout 3, which had a great soundtrack, could get tiresome sometimes, so I would download alternate radio stations that people had created. None of them were 'great', but it beats listening to "Maybe" by the Inkspots for the 100th time. Skyrim has one of the best original soundtracks that I've heard. Oblivion's music wasn't too shabby either. At some point, though, regardless of what game I'm playing, I'm going to turn on my own music, or go to Pandora.
The only bit of Skyrim's music I remember is the theme. I think Jeremy Soule does great themes but I don't really recall anything he's done that has stood out otherwise. Kirill Pokrovsky is one of my favourite composers (Divine Divinity, Beyond Divinity, Divinity 2, Divinity 2: Flames of Vengeance, Divinity: Original Sin and (I think) Divinity: Dragon Commander).
I haven't played in a while, but I swapped out the standard theme for Malukah's(sp?) version (There's a mod for that). BTW, I also kinda like Civ 5s music as well. There probably are other games that have had scores that I have liked. I just tend to not remember them.