I think the rundown is basically this: Right now Intel is pwning. A little later AMD might pwn back. But for gaming both the Phenom and i7 cpus perform close enough to eachother for no STAGGERING difference in fps increase/decrease between them.
However, with quad core processors having been around for a while now, more current/future games will be quad core optimized. When that happens more, it's safe to say that i7's will outperform the Phenom processors.
Simply put, definitely go with the i7's if you can afford to, because when games become more optimized for today's cpu technology, they'll break completely away from the Phenom's.