I think that's a problem that a lot of entertainment mediums (tv shows, movie franchises, anime, game series, etc) have, going on longer than they probably should. But hey, if they're still making money, they'll still be made, yeah?
I tend to agree, though, with the exception being Final Fantasy stuff. I like how each game had their own unique systems in place, until they took away the turn based aspect. I wish they would go back to being a little more generic gameplay wise and less "innovative."
Which I know they do that with the Bravely Default titles, so I guess I can't be too grumpy about it.