Rent DmC, don't buy unless you know you'll enjoy it. DMC3 and 4 are still better. 3 in particular is leagues above DmC and this is coming from someone that likes DmC.
I just finished DmC last night and I enjoyed DmC and DMC3 about the same amount. They are both excellent games so I think DmC is a definite must buy for people that enjoy action games. RE6 would be a "rent first game", not DmC.