C2 is best. If you don't want to study programming for maybe 2 years.
Unity is a great cross-platform mobile tool; however,
you need not only coding skills, but lots of money.
Engine has a price, each function has a price, each exporter has a price,
and maybe you have to hire a professional 3D artist(no matter you want to build a 2D or 3D game.).
If you don't want buy its toolkits, you may spend more than 1 month to do what C2 can do in 1 hour.
I'm not sure Android(too many devices and specs).
In iphone4S, the FPS of my C2game is faster than Chrome/FireFox without webgl,
and the same game performed 2FPS on iphone4/ipad1.
It takes time. They are really doing something.