I have played many single player games and I can almost guarantee I'll be spending 20 times more time in Overwatch than those games. Depending on if you're interested in MP shooters, many will easily get hundreds of hours of enjoyment out of this game.
A game shouldn't require a campaign, co-op and MP to be sold at a AAA price tag. As long as it's fun enough to provide many hours of entertainment that justifies the price tag, it deserves that price tag. And Overwatch for me is easily one of those games that is worth its asking price. The perception of value differs from person to person.
As a side note even though there are microtransactions for cosmetics in the game, all future heroes and maps will be free for everyone, which to me is a good model to have.
