I was thinking somewhere between an "M" and an "R". Then I actually filled out the rubric and came up with a score of 102, which would put it at the upper end of the "M" tier. Sounds about right, not a perfect port but nothing to really be upset about.
2K15 is the best basketball sim game of all time IMO. 2K14 might be if you count modding, because of something like UBR, but I'm just talking about the raw, untouched game. The gameplay is so much better than 2K14 even. And then with MyLeague on top of that, it's such a deep game. I have high hopes for 2K16, though. If you take 2K15 and add ProAM with the ability to create your own arenas and stuff, god damn.
I like 2k11 much more to be honest. Of course 2k15 is better in many ways, but 1st they got rid of good things over the time (online league including the community homepage........) and 2nd I always found the gameplay much more fair in 2k11. In 2k15 it always seems like there is happening so much crap in a game. Things to keep games close artificially and other stuff, I really don't like.