Thing is, I've yet to see a REALLY successful C2 game in the play store/app store.
I think this was discussed a few time here, so here goes my opinion.
I think the misconception is that one always think that a game engine play key success factor in getting successful. However, it is actually not related, it depends on luck and "what" actually published by C2 user. Let's think about it, rather than keep looking for whether C2 games has made it out there, why not challenge ourselves to be "The First One" to be successful. If we keep looking this way, and given up just because no user made it big with C2, it's like a dog chasing it's tail.
Engine will always be an engine, being creative and appealing is what we should be aiming for. In the end, C2 is just a tool.
Analogy: Heck, I dont think a success factor of a novel is determined by the tools used by the writer, it can be notepad, ms word, or just pencil and paper, but CREATIVITY IS.