As stated above, its no longer about MHZ frequency but out of the chip itself.
The price point usually reflect perfectly how it will perform.
You have to keep in mind that playing game is not just CPU. the Graphic card is an even bigger factor.
For an average gamer, an Intel Core I3 or an AMD FX Chip will do a fair job if paired with something like an AMD Radeon 6750 or better or an Nvidia Geforce 550Ti or better.
Notes:
AMD Graphic cards
4000
5000
6000
7000
First digit indicates the generation. 7000 being the newest cards.
4850
5650
6870
7950
Second digit indicates the "performance level"
So a 6670 is slower than a 5770 for example.
The third digit will indicate lower end or higher end of that specific range.
So a 6750 is slower than a 6770 but the 6770 is slower than a 6850...
It's rather similar for nvidia cards.
Refer to this to have an idea where videocards stand
http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-7.html