I think the main problem is that when Capcom has a good idea for a game, they keep the same formula as long as they can until sales drop significantly.... Then they either stop making games from the series or when they do change the formula, they change it so drastically that you don't even recognize the game anymore.
The worst Capcom example of using the same formula is Mega Man, every Mega Man game considered good are basically the same thing, they just change level design and powers. Hell, Mega Man X8 for the ps2 plays the same as Mega Man X for the snes. And when Mega Man was at its peak, they made one game per year... So they don't change the formula, they saturate the market with Mega Man games and they expected the series to sell forever?
With Resident Evil they were doing the same thing, but they changed it so much in 4 that it lost its essence... Capcom is great at making fresh new innovative games, but they are not always good at keeping a series profitable through the years. Well, they do have Ace Attorney which they've been doing a pretty good job maintaining, and they did some experimenting with the formula with Ace Attorney: Investigations and Dual Destinies. I hope they keep this one going