Some one managed to create a full customised map of Metal Slug using Starcraft 2 game engine. Like the commentator in the video has said, the engine is not built for this kind of playing, however, yet it has been created still. It took the commentator 35 minutes to complete the entire map. From the looks of the video, it is a map worth downloading and playing.
So here is a +1 reason to get Starcraft 2. Download link. And oh, need I to add that it is only Act 1 of the entire series? This version is just the beta version. Once Starcraft 2 is officially launched, the full version will probably be out. The full version will feature 2 players functionality. This means that you can play with your friend over network.