What's wrong with my videos.

What should I do with my videos for best selling? It is necessary to raise the technical level of the issue, I mean to buy some kind of better camera for filming. Now I'm shooting at Canon 600D and 7D. Should move in increasing artistic performances?
I would be very grateful for the criticism and hints. Thank you!

You just need to make many more. Your technical level is fine. Nice quality. Keep in mind you are going against millions of other clips, so the more you put up, the better your chances. Your cameras are fine as well. It's not the camera, but the person behind the camera that makes for good content. And you are fine in regards to that issue. :)

Thank you very much for the advice!