PC game profits started to decline when publishers abandoned this community and decided to opt for multiplatform, designed-for-console releases.
By this logic, high budget, PC exclusive "hard core" oriented titles (and by this I only mean no Sims or Barbie) should do noticeably better on PC than the multiplatform games do.
It's trivially easy to point to examples of multiplatform games that outsell PC exclusive games - Bioshock and CoD4 leap to mind.
My feeling is that Stardock's games are selling really well for them, which is awesome, but I seriously doubt they're outselling Bioshock, CoD4, Orange Box, etc. on PC.
My point in listing these games isn't to argue their merits vs. one another, just to point out that THIS is the data that publishers are going to look at when deciding whether or not to make their games PC exclusive.
The fact that even Valve is making console games now has to be significant, right?