I think Sundown put it best, "So long as the physics, mechanics, and animations look correct, the success and trigger rates can be tuned." When a defender's going up to contest a dunk in a video game, timing, ability, rating, momentum and likely a number of other variables are taken into consideration. What I was saying is if those variables add up to the game allowing me to complete a blocked shot, I'd like it to look authentic and real, and at this point that seems it'd need a two-person animation.
Similarly, if I'm a sitting duck and due to my poor positioning and the fact that I'm controlling Muggsy Bogues, I'd rather have a two-person dunk-on animation occur instead of the dunker slamming as if I weren't even there with my virtual Bogues just jumping straight up and down with his hand straight up (or heaven forbid, being slid backward in mid-air 2K13 style).
A couple of examples - one would be at the 1:58 mark belwo. Vernon Maxwell has no chance. There's contact, but he's just jumping straight up and down and he's slide backward in mid-air. It's established he's not going to block the dunk, so I am stating I'd rather have Maxwell interact with O'Neal realistically, even if he's going to fail due to his poor positioning (and the fact he's Vernon Maxwell trying to block Shaq):
On the flip side, the number 1 play in that video (3:25) is a two-player animation (or as close as 2K13 got to one). I find those interactions much more aesthetically appealing.
2K12's dunks in traffic looked much better in my opinion due to the aforementioned animations: