The only thing more fun than playing a game is bragging to people about how much more fun you're having than they are. When they have access to the same game you were dangling in their face, you have one less thing to brag about. Maybe you hyped a game up to an insane degree. It's an unspoken rule amongst owners of the same platform to make the game seem better than it really is (Alan Wake/MGS4, for example). Now, the competition has that same game and they're going to know just how full of shit you are.
Gamers want to be part of the winning team. How can you win if the competition has everything that you have? Find the one teeny tiny thing that makes your console different and make it seem like the greatest thing ever? No, it's much easier to say "I can play this game and you can't."
Do you have any idea how many walls I punched when I found out that Street Fighter 2 was going to be on Sega Genesis? None. But I should have punched a wall.
