Take a look at the past Street Fighter games. Despite the fact that Capcom has made a lot, 4 of the 5 titles are versions of Street Fighter 2. The franchise has been dead since. The problem is that
- Capcom flooded the market. They milked one game, and buyers got bored. Consumers like sequels becuase it meets two essentually requirements. The sequal is more of the same (which is why the consumer bought the first title unless they returned it) and its new content. You need both for a successful sequel. Capcom did not have the latter, and the franchise died
- Capcom focused on it's core consumers. Rather then try and get new players to enjoy Street Fighter, they catter to the old fans. This nis why Street Fighter is one of the best tournement games, but sells horribly. This is why Smash Bros must never be focused on as a tounrement game less it face the same fate. You can tell by playing the game. It's more of the same while adding so many features that only competitive players will take advantage of.
I'll be honest, the sales of SF4 were better then my predicition.