InsideHW.com has compared gaming performances of Core i7 and Core 2 platforms. Here's a bit:

Should you make a transition to 1366 pins or not? Our opinion is that, in this moment, it's not worth it. It is not good decision to invest so much money into new platform (CPU, motherboard, memory...). We suggest you to invest smaller amount of your budget into new graphics card rather than in completely new configuration and that way you would get better price/performance ratio. Of course Core i7 platform is there for hardcore gamers as ultimate solution. If you want to achieve maximum FPS in games, you should go for Core i7 platform. For all other gamers you should wait a little bit for AMD Phenom II CPU that should be positioned somewhere between Core2 and Core i7 when it comes to gaming performances, but with price tag closer to Core2 CPUs. Also Intel announced Core i5 CPU series that will have integrated PCI-Express controller and that is something really worth to wait. There are rumors that this CPU will be great when it comes to gaming performances. Until then take a look at results, and your wallet, because sometimes it is wiser not to be enthusiast at all costs.