Question: Is it possible to get an 'S' rank in Resident Evil 6? If so, what are the general requirements? I know some will probably be subjective to the level (time and enemies) but what about accuracy and deaths? is there a set rule for an 'S' rank? (assuming it is even possible)

This was the case in most of previous games. So far my best is an A rank, and I suppose the closest I have to knowing if an 'S' rank is possible is that my number of deaths was at 1 (which gave me an 'A' rank) and I wonder if 0 deaths would be an 'S' rank.

Anybody got anything better than an A?

Answer: 
You have to get rank A in 4 ratings to get an S rank.
Simple answer, you just need an A rank in the 4 categories. You can't get an S in each category, as obviously a zero death would count as an S, but if you get a B in any category, you'll get an A or less instead of the S.