That is what they do. Most other gaming companies just keep a few ideas to put in the next game but add new ones as well. Whilst Ubisoft, take Rayman for example, Ubi kept many characters and bonus things like Teensies and Lums as well.
But i just think UbiSoft don't know any new idea's because they had too many allready, that's mostly why a gaming company is giving it away, and that doesn't matter me because Rayman to new company = new idea's.
Yeah, Ubisoft like to have new ideas, as I gathered in R3...
However they are not allowed to even read the ideas of other people. If they did, they might like the idea and want to use it, making it not their idea.
I hope Rayman 4 will be similar. Rayman 2 was an excellent example of a game everyone who played it likes it. Even now, I'm still quite attached to the game.