Having now finished Leon's campaign and half of Chris's, I will say that we are at a point now where we literally have no idea how a new Resident Evil game will play. RE4 is different from RE5, and now, RE6 is yet another twist to the formula. Revelations was wildly different too. Who knows what we will get in the next one.
This game feels like they tried to appease everyone, but by doing so, failed to find a unified direction. Instead, it's a mishmash of everything from the entire series into one. While I am enjoying it as a longtime fan, I fully expect it to be critically panned... and end up being the worst of the post-RE4 games.
I actually don't think it will be. Critically, probably (well, it'll be above Operation Raccoon City, maybe above Darkside and Umbrella Chronicles). But among fans I think the game will be split, but in the end be regarded as better than RE5 by most. I agree with the mishmash, but the more I've played it the more everything has felt coherent rather than the opposite which I thought might happen. With that, I believe the highs of RE6 are better than RE5's highs, and its stronger horror and action elements as well as variety keep it above RE5. I can say I've enjoyed the horror sections and the action sections of RE6 far more than that of RE5, and this is coming from someone who did like RE5 (as a co-op game, I felt it was the weakest of the main RE games, however). Even as someone who actually really liked the bosses in RE5 a least, I feel RE6 has stronger bosses (and a lot more of them).
The only area I feel RE5 may have RE6 beat so far is Mercenaries (which could change if more is added or becomes available once RE.NET is launched. I enjoyed Mercs Reunion a lot more than I did regular Mercs for some reason).
This game is polarizing, there is no doubt to it, and critically I think on sites like Metacritic it will sit somewhere in the 70s range (with high and low scores all over the place). But I have a feeling after spending more time with it that this game, for me and I believe more than not will feel like this to be the better game
This is all preference of course, and I have no idea how this game will stack as well with RE4 and Revelations in the mix. I enjoyed RE4, RE5, Revelations, and RE6, but all for completely different reasons.
Resident Evil 6 isn't a bad game, it just is a completely unexpected one and a title that kind of goes all over the place.
(Also as I am now finding out, it is a REALLY fun co-op game. It already had a much better single player experience than RE5, but now playing co-op and dang this is a lot of fun with friends.)