PC is the superior platform as far as performance and it's not even close.
Take a look at the specs for an Xbox 360:
-3.2 GHz PowerPC Tri-Core Xenon
-500 MHz ATI Xenos (Further research says it can reach 240 GFLOPS, which is a pretty standard way of determining performance since they don't show the amount of memory for the graphics chip.)
-512 MB of GDDR3 RAM clocked at 700 MHz with L1 cache of 32/32 kb and L2 cache of 1MB
Now take into consideration the Xbox 360 is close to 7 years old. The hardware for the most part hasn't changed in 7 years. Now take a look at my current gaming PC:
2.8 GHz AMD II Phenom x4 overclocked to 3.4 GHz
ATI Radeon HD 6850 256 bit 1 GB GDDR5 775 Mhz overclocked to 900 Mhz
16 GB of DDR3 RAM clocked at 1066 Mhz
Pretty much what I'm getting at, my gaming rig blows the 360's specs out of the water without lifting a finger. When games are properly designed for the PC, the graphics are crisper, better performance, better load times, just generally overall it just looks better.
There is no proprietary anything when it comes to the PC platform, I don't need a special disc drive to install game, and if my disc drive goes out, it costs $20 to replace it compared to having to send a 360 in to get fixed and spending a lot of money for shipping and repairs. Those repairs will take quite some time as well according to past experience, meanwhile I can order the replacement part and have it in within a week.
When it comes to consoles, you need to wait years before you get an upgrade in hardware. The abilities of the 360 have been maxed out for some time, and only an upgrade in equipment will allow game developers to really push the envelope anymore. This is why you hear the old cliche when discussing PC's "Yeah but can it run Crysis?". Crysis was designed specifically for the PC, and it was made to push the graphical capabilities of the PC at the time. Compare CoD on a 360 and Crysis on a PC, and you will truly see the difference of designing a game for the PC rather than a console. Game Developers have far more room to play with for performance and graphics on a PC.
Now there are some issues that need to be addressed with all this. Game developers 95% of the time develop games for the console first, and then come up with a half assed port to the PC. This is infuriating as the graphics are still limited to the consoles at this point. Sure the port may give you the ability to increase graphics performance, but the gain is not nearly as much as it should be. Skyrim looks absolutely beautiful on my PC, and far better compared to the 360 version, however if they had designed Skyrim for each platform individually, the PC version would likely have been even better performance wise.
Another issue is that many game developers believe that PC gaming does not bring any money in. Back in January 6th, Steam announced that sales had increased 100% for the seventh straight year, boasting over 40 million users and delivered over 780 petabytes worth of data. Let me break away from the doldrums of my lecture and say that's fucking insane. They have doubled sales every year for 7 years, and 40 million users. That's the same number of users on Xbox Live, the difference is most people just use Xbox Live to play games, people use Steam simply to purchase games. So that all being said, is it really a good idea to treat PC gaming as a second cousin when you have the same amount of people on Steam (and note this is just Steam, that's not counting EA's Origin and simply purchasing games outright from a brick and mortar store, or Games for Windows)? Take a look at Blizzard, they rake in so much money that they can afford to simply take their sweet time developing games for the PC. Diablo 3 has been in development forever, yet by the time they're done it's going to be a smash hit. PC gaming is starting to hit its stride and perhaps game developers will catch on and start actually designing these games to fully implement on the PC rather than just porting games over. Maybe we'll start seeing games like Crysis fully designed to utilize the massive performance advantage the PC has over consoles.
Oh and did I mention the keyboard and mouse is still an amazing combination for games? FPS gamers on a PC still swear by them to this day. Now you think just a simple keyboard and mouse is all you need, but if you want that edge depending on your type of game, you get a mouse with a quick response time, high DPI, and of course customizable buttons. Keyboard wise you can get a mechanical keyboard which improves response time, or if you're an MMO player, grab a keyboard with multiple buttons for macros and automate so much of your attack cycle with the press of one key. The gaming keyboards and mice that are out there are tremendous, and as an owner of the Razr Deathadder mouse and Logitech G15 keyboard, I can tell you that there is a big difference between gaming peripherals and a standard keyboard and mouse.
Overall the customization and performance of a PC puts it's capabilities far and above a console. It will be interesting to see the new generation of consoles if they will try to take advantage of the major advances in components that are available or if they will continue to put lesser hardware inside of them. Even if they do up their hardware to a current gaming PC level, PC's will just develop better hardware shortly after and once again their specs will decimate the consoles.