It mainly seems to happen with 3rd parties. I think they focus on medium-term profit while 1st parties consider longer periods. Just see what's happened to the credibility of the Sonic franchise since it moved away from 1-3 games per gen.
They should realise that when they have a fantastic new IP like Assassin's Creed or Guitar Hero or Tony Hawk, these franchises can be sustained in the same way Nintendo has been sustaining Mario, Zelda etc.
Look what happened to Tony Hawk. Tony Hawk 3 was a AAA must buy game. A system seller. Guitar Hero is dead, and Assassin's Creed will probably end up with the likes of Tomb Raider.
pfffft.







