how exactly did they fuck up Civilisation? the fifth one was great. okay, the diplomacy wasn't that great, and it was generally easier, but it was still a great game.
If you can't see how they fucked it up, you didn't grow up with Civilisation like some of us did
Deadmeat, you lovable cynic, you. Having played all of the Civ games at one point or another (Civ 1 retroactivley, but the rest within the timeline). I have to say that I personally think Civ 3 was the peak of the series, but in all games they have improved. Civ 3 was the peak of diplomacy (taking most of its cues from Alpha Centauri), Civ 4 had the religion and corporations which added extra flair to it, as well as making the systems a lot less obtuse on the whole. Civ 5 had the shocking innovation of, for once, making combat make sense. The combat in every civ game but the fifth is some of the most headbangingly frustrating gameplay I've encountered in many games. I play a cultural/technology victory playstyle in the previous games. This isn't because I prefer them, but because the combat system is utterly retarded. Spearmen should never beat tanks.
EDIT: I also want to point out that Civ 5 has yet to recieve an expansion. Civ 1 is the only who didn't have the additional benefit of recieiving aftermarket support, and lets be honest, when (probably not if) Civ 5 does get an expansion, it'll make it a better product.
Additionally, none of this is really relevant to Firaxis making an X-COM game. This actually gives them a chance to work outside of their usually grind, which gives them a lot of room to be creative and do new things.
TLDR: Old is good. New can be good, too!