I think people are talking about two different things, here.
There's the cinematic killcam like Skyrim, then there is the PvP CoD-style killcam that PvPers talk about. Obviously not the same thing.
Correct me if I'm wrong but I never had a killcam in either Skyrim or in Fallout 3/NV when there still enemies around, it always happened against the last standing opponent in the fight or at a stealth kill in Skyrim. (Hmm, maybe in Fallout it did happen in combat too but I don't think so, but I'm pretty sure I only got it against the last standing opponent both on PC and on PS3.