Personally, I don't see how, considering that it's easy to find these games for free on other sites. The only options I can see are either using ads or making the software shareware, allowing players to play for a certain amount of time or a certain number of levels before having to pay.

Hey Umen, there are lots of online game companies doing very well right now. Check out Zynga for an example. I believe most of them are monetizing through a combination of advertising, as well as selling in-game items and features to the most engaged fans.