Well my two cents:
Get your game on an app store.
Problem: Massive competition depending on the app store. Apple app store for example is very saturated. Your game must be in above average level at min, and you MUST spread the word about how cool is your game on the four winds.
Freemium Games : Free to play game, but you can purchase in-game improvements for your character for example.
Problem: You have to plan things extensively and come up with a good business model. Like what things would be paid and what things would be free. How far free players can go in the game compared to paying players etc.
But the most important thing is : Your game must be good. How good ? The players must not only be thrilled by your game on first look and first play but be compelled to come back to it again and again. So it doesn't matter, you could as well make a site for your game and put a big Buy Now! button if it's good enough.