The reason to play on PC is not because it has better graphics, at least to me. I play on PCs for many reasons (but I also have a PS3 and play it too). Basically:
- Different types of games. In consoles, you have mostly shooters, sports games, 3rd person action, brawlers and platformers. In PC you have other genres that are lacking in consoles, like strategy games, MMOs, tactical games, adventure games.
- Cost. First, to play online you pay extra $50 or more a year in consoles. Games are also more expensive (with the price of one console game I can buy like 5 games in Steam).
- Mods. I love mods (and free mods at that).
But like I said, I also have a console and play games there too. Sometimes I spend the afternoon playing some console game, sometimes I spend the afternoon playing a PC game.