The thing is, Capcom games aren't famous for the sort of thing that makes regular releases good.
By DMC4 people were already complaining that the series was stagnating (incidentally, after a year of releasing sucky trailers, the most recent DMC trailer actually looked good. (Except for Dante himself, could still do with being a bit beefier) Combat finally looked like DMC combat, world changing looked fun and most importantly someone threw a caravan at him and he jumped through the first window got dressed in mid air and came out the other side on his feet. This is what DMC is meant to be. Dante is the man who sits down and answers the phone in ridiculously awesome slo-mo)
With fighting games it splits the community and tournament scenes, ruins the process of balancing and makes the games fairly pointless (I mean fighting games don't have much variation as it is, and what they do very has to be basically reinventing game mechanics in clever ways)
Do people really care enough about Lost Planet?
They could do it with Resident Evil though. The thing is they release so many spin-offs, they basically do already