well, a lot of people just love the passion that the players show and love it more than the NBA (which a lot of people hate - too much money and no passion) and a lot of people root for their Alma Mater. Not to mention the pools and money.
Most of the time, NCAA > professional.
GMU - wow, i couldnt believe what they did, and yea, Butler, Skinn, et al will probably not become stars in the NBA. But they were in the spotlight and the hearts of millions of kids and adults and had everyone rooting for them. Sometimes the team that just isnt as talented but has a lot of heart cant win. Its too bad they didnt win. But i wouldnt worry about GMU. Laranegga is a great coach who recruits well (i think all 5 starters are from Maryland) and smart. And a lot of people just jumped on the GMU bandwagon, too.
This is how i felt last year when my Steelers lost to the Pats, and when my Caps lost to the Red Wings in 98.