Just a link today to a nice article about the prospective economic impact of hosting a Super Bowl.
In general, I would say that if a region can get a Super Bowl, that's probably not a bad thing. Just as long as they're not paying to bring it there. The issue economists usually have with hosting large events isn't that the events are bad--there is much good that can come from them--but that cities generally try to outbid each other for these things. In terms of the economic impact they have, the bids are always much, much more.
Of course, some events can crowd out economic activity (imagine trying to travel into Chicago for dinner at Ditkas if the Olympics were in town). Ultimately, this could create a net negative result, too.
The final quote in the article is rather entertaining as well.
Hat Tip: The Sports Economist