Basically...
The big Midlands rivalry used to be Albion - Villa, because we were the 2 Midlands clubs constantly in the top division. Wolves versus Stoke used to be the Staffordshire derby.
Then they moved all the boundaries, so that Wolves, Albion, and Villa were all part of the West Midlands.
We went into decline, just after Wolves did, and because we ended up playing each other a lot in the championship, combined with the feral nature of most of their support...familiarity bread contempt. All the while, the Villa condescended to both of us, and Blues. Blues started to really come into play at this point, I think, because nobody from the older generations really seems to give two s**** about them.
So now Blues view their main rivalry as Villa, because in recent years they have been able to play them on a more level footing. Wolves see their main rivalry as us, because we're closer than Stoke, and familiarity has bread contempt. Younger Albion and Villa fans therefore see Wolves and Blues respectively as their main rivals. However older fans still see each other as the big derby.
With Albion now in a better position than Villa, but both in the Premier, I can see it being the regions big derby again...which will just annoy the hell out of the Bluenoses and Dingles.