I'm shocked that this isn't a bigger fight, post-wise. It's neck-and-neck in the votes. Reminds me a bit of Sephiroth vs. Bowser from last year.
To be honest, I could see either man coming out on top. Both are big bad bosses with big bad fisticuffs and big bad magic. I really want to see arguments from both camps. I know we have lots of fans of both guys on this forum.
On one hand, you have Shao Kahn, one of the coolest, cockiest, and most powerful bosses in any game. He's the announcer for the Mortal Kombat tournament, the ruler of Outworld, and wields a giant hammer. On the other hand you have the corrupt commander of Shadaloo, M. Bison, who has powerful magic blasts and dark energy.
I have to agree with the above poster that Shao Kahn's taunting would really play a huge role in this match. That could give Bison the edge he needs to attack Kahn, but Kahn is no fool and would probably not make many rookie mistakes. You don't get to Final Boss status by being too dumb.
So come on, let's hear some reasons from both sides!