Hmm. This thread actually has some good information in it.
Thumbs up to both razor and Toss for providing their info. I had no idea that PhysX had gained so much marketshare.
Some key issues, I think, are:
1) How many of those PhysX titles from razor's graphs run on the GPU exclusively (this would be Nvidia's selling point.)
2) How does performance with multicore physics w/ a CPU compare to single-GPU physics (Toss answered this one with his graph.)
I still contend that most of the best physics effects that I've seen were ran strictly on the CPU. HardOCP comments on this here when demo'ng Ghostbusters on a quad-core with the Terminal Reality team:
And I've yet to see explosions and smoke effects of the quality of Battlefield Bad Company 2, with physics on the CPU:
Notice that the engine is smart enough to know how much structural damage a building can take before it collapses.
From what I've seen of Metro, I just don't see any significant gains at all from PhysX in that game over what the above titles offer. In fact, I'm generally less impressed than I am with the CPU-physics games.