Are there any well known apps that have hit the big numbers(100,000+)? the only one I've really heard of is mortar melon.
I understand that a large portion may not of have active on the forums and not published the details of what it was developed in.
I think the issue with answering this question is possibly due to the mentality that the engine determines the end product.
Take Angry Birds for instance. Can you make Angry Birds in C2? Yes. Can you make it in Stencyl? Yes. Gamesalad? Yes.
It doesn't matter what engine they made Angry Birds in. The fact is they made a polished game and marketed it well.
Develop games in your browser. Powerful, performant & highly capable.
Oh yeah, there's absolutely no reason someone couldn't make a popular game with C2, I have no doubt there has been more we just dont know what they are :)
I think Notion Games's Super Ubie Land will be big as they are putting it on Nintendo Wii U. http://notiongames.com/