EA (licensing correction)Keith Schleicher sent in this:
The MLB license isn't completely exclusive. 2K Sports has a third-party exclusive deal. That means that if Microsoft had wanted to make MLB Inside Pitch (I believe that's the name of their baseball game they did a long time ago), they could do that. Nintendo could have done one for the Wii as well. It's probably a mater of resources and the cost of the license that they didn't create a baseball game.
Of course, he is entirely correct. I got the details of the deal mangled in my head, but the console manufacturers could still make MLB baseball games if they wanted to purchase the license. 2K was the only third-party developer who could make an MLB game. That was the degree to which their license was "exclusive."