This would be more understandable if Resident Evil wasn't already one of the biggest third party franchises out there. Resident Evil 4 sold 7.39 million across its 3 machines, and Resident Evil 5 sold 7.72 million across its 2. There aren't many bigger third party franchises than that.
The only third party franchises I can think of that are substantially bigger are Grand Theft Auto, Call of Duty, The Elder Scrolls, Battlefield, Sonic and Assassin's Creed. (This is ignoring games which fall into a completely uncomparable genre, ala Just Dance).
Resident Evil sells more than Mass Effect, Uncharted, Zelda, Final Fantasy, Gears of War, etc. Staying as the king of the horror genre is a far safer plan than trying to challenge the biggest games the biggest franchises the industry has to offer (well, barring Nintendo at least).
It's a rather odd choice.
