Have you already chosen the rest of the parts in your system?
For gaming I'd go with an i5 over an i7, the i7 will give you no noticeable difference in performance for the foreseeable future. By the time it becomes useful for gaming, you'll probably need to replace it anyway.
I'd also get a haswell cpu (4xxx) unless the ivy bridge (3xxx) is quite a bit cheaper.
The main thing to consider if you're not overclocking is what connectivity you need. How many fans will you be running? How many hard drives/ssd's? Do you need any specific features (such as legacy PCI slots, etc)? Also, do you need a mini ITX or micro ATX board, or are you using a standard ATX case?