I think the difference between "playing for fun" and "playing to win" does not mean these terms are mutually exclusive. Someone who plays for fun could be overwhelmingly good at a given game, but they enjoy beating the crap out of other players. The ones who cry foul on these players are merely the ones who don't have a grasp of the game mechanics on par with the one player who destroys everyone. What they're complaining about is that their fun has been ruined because they stand almost zero chance of being effective against the good player. However, if your "play to win" attitude means that you sulk and pout if you aren't the top player of a match (ragequit!) then I think you've gone over the line from fun into competitive jerk.
For example, I'm really good at Guitar Hero/Rock Band on guitar or bass compared to basically everyone I know. I consistently beat them all in any kind of competitive mode, but I have fun merely because I'm able to play the song at a high level, not because I crushed someone else. If I do happen to lose, I don't throw a hissy fit, because I know there are guys out there who can 5 star Jordan (Dustin, you punk) on Expert.
For example, I'm really good at Guitar Hero/Rock Band on guitar or bass compared to basically everyone I know. I consistently beat them all in any kind of competitive mode, but I have fun merely because I'm able to play the song at a high level, not because I crushed someone else. If I do happen to lose, I don't throw a hissy fit, because I know there are guys out there who can 5 star Jordan (Dustin, you punk) on Expert.