The problem is that Civ is turn based, it can become damn hard to stop, and it is a game for long / uneventful afternoons / evenings. I think trying it out, all the different possibilities of exploring technologies and ways of expansion is really interesting. Althouhg for some it might only be interesting once.
I'm not too keen on good graphics in C&C like games. But I found it a little sad that in generals you couldn't just change entries in the rules.ini to change system specs.
RS6 gameplay is, for my taste, actually a bit clumsy.
Well, and I didn't do FC in the hardest way. But it was compelling to me.