As a PC gamer I feel I should add my 2 cents.  
 
First of all, I do not own a current gen console. I have all four last gen consoles, but this gen I decided to go completely with the PC. 
I find it strange that people are saying the PC does not have a wide variety of genres to choose from. Yes, MMOs, RTS, and FPS are very prevalent here, but they are not the only ones available. There are plenty of racing games, puzzle games, platformers, adventure games, action adventure. A quick glance at the Steam Store will tell you that.  
 
That is another thing that is worth touching on actually. The fact that Steam exists. The gaming media loves to fantasize about a platform with no physical media. Well, that platform already exists. It's called the PC. 
 
I think if there's one thing I want to stress about PC gaming is that it is a very free and open place.  
 
New developers can make games with little overhead, and get noticed. The indie scene has absolutely exploded on the PC. Consoles have this as well, but the amount of volume of indie titles on the PC is overwhelming.  
 
PC games also have large mod communities. We have games that grow because other users have decided to put their own time into giving other players more game to play. If you do not think this is significant go look at stuff like Pirates, Vikings, and Knights. This is a situation where someone took an existing game and made something completely different out of it, and not only that, but they gave it away for free. This type of thing just does not exist on consoles.  
 
Then there is stuff like Garry's Mod. There's a game that is made up entirely out of things from existing games, and it is supported by a lot of dedicated players that make stuff simply because they want to.  
 
There is also the matter of custom maps. I remember the first time I played Counter Strike on Lego Land. Yes, a map made of Legos. This concept sounds ridiculous, but it was really fun to be able to run around shooting each other on such a silly map. On a console, they would never make a map like that. The developers are dedicated to making sure the maps fit in with the rest of the game. And even if they did, they would charge you for them. 
 
 I love fighting games. Specifically 2D fighting games. Now I know people like to pretend there are no fighting games on PC, but this is simply not true. Street Fighter 4 is on PC, and do you know why? Emulators. Yes, you can argue about the legality of using roms and playing games through MAME or the like. But stuff like MAME allowed PC gamers to play almost every major fighting game (and a lot of non-fighting arcade games as well) that exists between the early 90s and up until just a few years ago. MAME also has a dedicated community constantly trying to improve the quality of the games, and get non-working games working. The point is, Street Fighter 4 came out on the PC because Capcom recognized that there was a community of people that love Street Fighter, but were not being sold copies. PC gamers aren't using MAME because they wanted to steal Capcom's classics, but because Capcom was not selling these games to them. Believe me, I probably would not have bought Street Fighter 4 had I not gotten hooked on Alpha 3 through MAME. 
  
I can also use whatever peripherals I want on my PC. You've all seen the videos of people using a Wiimote to play Half Life 2, but it does not have to end there.    Quick little fact about my peripheral collection. I have 2 Xbox 360 controllers (Regular Wired, and Ryu Fightpad), and a low end joystick that works on PC, PS2, and PS3. I can hook up the joystick and hand my friend a 360 controller, and we can essentially have a Sony controller vs a Microsoft controller. This is impossible on any other platform. The freedom we have to use whatever controllers we want is incredible. There are wheels, arcade sticks, flight sticks, regular controllers, all kinds of peripherals made for the PC, and we get to choose what we want.  
 
Backwards compatibility. I'm sorry, this is a bit of a low blow, but it's true. Most consoles do not have this feature, PC's have never really had to worry about it. While a console owner has to worry about whether or not their game from 5 years ago will work, most of the time PC users don't have to worry about if their game from 20 years ago will work. For games that are that old, stuff like DosBox exists.  
 
I see this has a gotten a bit long-winded, so I think I'm going to call it a night. But I just wanna say one more thing real quick. Most of the time the argument from the console side is always price and comfort. The PC is way more expensive, and games are more fun to play on a couch with a 50" screen.  
My TV is a piece of shit. How much was that 50" screen? 
What? 
I like my chair...