I will answer honestly seeing as PhotonBoy isn't being entirely honest. Older DirectX9.0 games (and even older ones from before) were only optimized to run on up to 2 CPU cores. Most of these titles, however, really only use a single core. So if you plan on playing older games, you'd think you might want a CPU that is capable of doing more work per clock (per MHz a.k.a IPC or Integers Per Clock). The thing is, older games don't require powerful hardware. So even a highly threaded CPU (like the AMD FX line) can run these games with ease. You will not get an unplayable scenario with the AMD FX 6300 or above in modern titles (as well as up and coming titles).
The AMD FX line is also far less expensive. So it has that going for it. As PhotonBoy mentioned the AMD FX line does consume more power and their CPUs do tend to run a little hotter. Its not much to be concerned about in the real world. I mean in most areas you won't even notice the difference on your utility bill.
Now with future titles, things get much more interesting. AMD have released an API (its a programming language used to code a game) called Mantle. This API is optimized for MultiCore CPUs. It alleviates CPU overhead while allowing the work sent to the CPU to be spread out more evenly across multiples cores. Under this API AMD's FX line is shining.
Now you may hear people say "So what? Only 3 games use Mantle". True, but Crytek has signed on (makers of Crysis), Electronic Arts have signed on and it looks like Ubisoft may be joining soon. These are companies which make video games.
But even then, Mantle's Adoption rate doesn't matter. Microsoft has now come out and state that they will be following AMD Mantle's path with their new DirectX 12 API. In other words... the future looks bright for the AMD FX line. So a CPU purchase, of the AMD FX type, is a sound one.
Also a CPU bottlenecking a GPU and Vice Versa doesn't matter so long as the frame rates are playable. I mean I usually bump up all of the graphics settings to the maximum my PC can take before the game is unplayable. I rarely use "standard" settings. I always hit the "customize" and max everything out.
So benchmarks shown on the web, never reflect the results I experience. I mean if you're playing a game from what 2003/2004 like World of Warcraft then ya... a faster CPU will give you better performance but when you're running at 100FPS or 80FPS it doesn't matter. The experience is the same.
Its up and coming games that will push your PCs limits. That's where you should focus in terms of the machine you will be building. Focus on what is just around the corner and tailor you machine to it. That means AMD Mantle and DX12.
No need for an Intel CPU unless you're a total performance junky with money to burn like me.