Start by watching this clip, I'll make reference to it shortly.
I've always believed that boardgames are something to have fun with, but they are also something where people can compete in a friendly fashion.
I suppose it boils down to this thought, if you don't play to win, what are you playing for? Now, don't get me wrong, winning isn't everything, but it is something. We're in the midst of a culture where everyone gets a participation ribbon or trophy. Excellence isn't rewarded for fear that we might offend someone. That's silly! Knowing that you do something well is character building, but more importantly, knowing that you don't do everything well actually forces you to examine yourself. It isn't enough to get a prize for playing, you should strive to do your best.
I'll step off the soapbox and bring this back to gaming. For all my statistics of games, the one thing I don't track are wins. That's because my ultimate goal when I sit down to play games is to have fun. One of the ways that I have fun is in TRYING to win. That doesn't mean winning at any cost, or becoming upset if I don't win, but it means doing my best in an effort to be better than everyone else. It also means if I can't win, let's play for 2nd, or 3rd, or however high I can manage. In co-op games, it's about working as a team member. I've had more fun in games of Forbidden Island where we all drown, or Fool's Landing sinks to the depths of the ocean, than I have in games where we win going away.
I played roughly 30 games of Settlers of Catan before I won a game. It made me a great player, because I saw what worked and what didn't. Some of those games were poor dice rolls, but I learned from those. As a child, I played a lot of games with my grandpa. He never let me win. This didn't frustrate me too much even as a 5 or 6 year old. What it did was make me rather excited when I finally beat him in a game, because I knew that I had earned it. When I was learning to play Chess as a 4th grader, my dad didn't let me win. He did help me make smarter moves, and eventually I won a match.
I submit to you that I am a better game player, and more importantly a better person because I was not simply allowed to win games as a child, and because I play the game to win.
It's a fine line between being competitive and being a good sport. I can't say that I always walk that line well, but I do my best.
I'd love to hear any comments about this subject, and perhaps get a good discussion going.