I already posted my own task manager log on here whilst running the Crysis CPU benchmark, in which the character is just running around shooting buildings and blowing up cars.
Tell me that's not using all cores? It's not using them to 100% because of GPU-limitation of course (1680x1050 all high, no AA), but it's using them all. At one point you can plainly see more than 33% load on three of them.
Just answered your own question as to why it's only using one core. No enemies and no physics.
LOL more flaw's in Helmut's claims, go easy on the young lad

Agreed, with more stuff flying about that's when core's get utilized. I can only presume with a better GPU the CPU is going to get pushed a ton more