So theoretical scenario, you're given a huge sum of money, something like 1 trillion dollars, but there's a catch.
You can only use that one trillion dollars to buy and fund a game development company of your choice.
Since you're the boss now, you can tell them what kind of game you want made and give them all the resources they need and more to make it.
I think most people have a game they really liked, but it didn't quite have the funds/time/polish/development needed to make it what it could have been, leaving lots of wasted potential. Good example is Just Cause 2, Co-op for that game would have been SICK.
What I want:
I personally would invest that money into buying Rockstar games. I'd make them develop a Free-Roam game with multiplayer that is JUST like the campaign. I was really dissapointed with GTAIV's multiplayer since there was nothing to do, and Red Dead got a lot closer but I want the whole shebang... 4-player Co-op story, side missions, ability to buy things from NPCS, EVERYTHING.