Quad-core or Dual-core CPU better for games?

[DsrtFx]

I'm just wondering officially how many recent games are tweaked for >2 core CPUs, is there a list made up of "These games work better on more than 2 cores than otherwise," I'm trying to decide between the i7-620M and the i7-720QM CPUs for my laptop.
I'm planning on playing mostly RTSs as well as a handful of FPSs on this laptop.

 

[DsrtFx]

oh hey, just found out that the GPU that i was going to also use, the nVidia GTX 260M, apparently is incompatible with the 620, so 720 it is, then!
i feel sooo n00bish...