I think there is a huge market for 2d PC games.

I have seen boys play free 2d scrollers on the internet for hours without getting bored. The problem with the free internet games is that they are small screen with limited levels and lots of ads. They also take up internet time and for families that can be a problem.

Parents like the 2d scrollers because it is a compromise. the young boys want to play halo and the parents don't want the realistic violence the scrollers seem to be a good compromise.

So if you can make a 2d scroller with interesting levels that can be distributed cheaply via internet or on the budget aisle, and can be easily installed on a laptop or the families second computer and with good marketing I think you can be successful.

And if you make one where you save kittens from monsters you can break into the girl market.