I think that this thread goes to the very heart of being a sports fan, and how people deal with the inevitable disappointment that comes with signing up to root for a team.
I don't think we can ultimately control how we respond emotionally to wins and losses. It's sort of at the heart of who we are as a person.
I do think that things have changed over time. People seem more passionate about sports, and that's both good and bad. I think that the attitude that only a championship signifies a successful season, and that everyone else is a loser is a fairly recent trend, that only helps make people more unhappy.
I'm not taking sides in this debate, I think it's very difficult to change our reactions to these things. But it does seem very Seattle-like to complain when your team is in first place, just as people are very unhappy with a Seahawks team that finished the last three seasons with winning records. I think that a 9-8 or 10-7 record is a sports fan's Rorschach test on whether you're a glass half empty or a glass half full guy.