Well, I think sequels have always been milked a bit in this industry. Super Mario 2 & 3 on NES, the ton of Tomb Raiders, Spyro and Crash games on the PSX, even the three Panzer Dragoon games on Saturn. And the Final Fantasies and Dragon Quests have been rolling along for some time...
Notice I lumped good and bad examples of sequels above. It's all about the quality of the individual sequels and how they improve and differentiate themselves from previous titles.
For the most part, I think the qualities of sequels in this gen has been pretty good. But we're still early on. Usually series can go downhill after that second game...
