for people that cant do all the real fancy stuff in the dunk contest because of keyboard use i have a suggestion. Its not as much fun but if your a fan of realism you will like it.
play the contest on rookie mode and what you will see are dunks that are in fact very realistic to what you would expect to see in real life...and therefore it is slightly easier to keep up score wise when you pull your dunk off.
the best dunk ive managed is between the legs reverse jam which got me a 49.