RE: Dishonoured, I think the most direct comparison, game-wise, this generation would probably be BioShock (new IP, sort of "quirky" even though it takes place is a very common genre, apparent emphasis on narrative and world, from a major publisher but not THE BIG ONES, etc)... and BioShock debuted at 490k--so pretty much exactly equal sales-wise.
Now you might debate overall scope of marketing campaigns, whether the stealth element changes the basic value proposition, how BioShock debuted on 360-only versus Dishonoured on both, etc... but basically I think this comparison bodes pretty well for Dishonoured.
With XCOM, I think the best comparison is Civilization Revolution, with the quid pro quo that CivRev had some IP recognition going for it in a way that I'm not sure XCOM did, and also with the quid pro quo that XCOM had a PC release. CivRev premiered to 146k, so again I feel like XCOM comes off doing pretty well in that comparison. I don't view 116k as abysmal, and I'm 100% positive that the game didn't have anything remotely approaching a typical "AAA MEGATON" budget.