I'd have to agree with The Faceless Master, it's a two-way street. Microsoft can't just come in and tell a company that their game is being ported (though I'm sure they'd like to). I mean there was absolutely no way EA would have let MS make their own version of Madden with online play a couple years back for example. Both parties have to be able to agree. Some companies guard certain properties very jealously, and some companies have an overinflated opinion of the value of their properties (which might be justified in certain cases), making it pretty hard to justify the price.
And depending on the situation, buying companies may or may not be a "waste". I mean they reportedly bought Bungie for $50 million, which was a huge bargain. And then there have been other deals where the economics really don't make sense at all.
But in general, I kind of agree with you BeOnEdge, though not just for MS or the 1st parties. I'm surprised there isn't a little more dealing going on between 3rd parties. Particularly, I would think there is a bit of an oppurtunity for western publishers to bring more Japanese games to the Xbox, and Japanese publishers to bring more western games to the Cube. For example, since Capcom is kind of lukewarm towards the Xbox, and Take 2 isn't big on the Cube, they could probably benefit from handing off some of their games to each other.