I think this is good from a marketing perspective. You've hit the important points:

- State the problem - Show the solution - Indicate the value-add - Prompt for the desired action

Is this convincing enough? I'm not a good person to ask. I don't play minecraft. Though you juxtapose your solution against Dropbox and that only benefit I see you offering above Dropbox is a way for users to "display" their minecraft world on the web. The real question is if people want this. I'm not sure. But other than that, I think you hit the nail on the head pretty well.

I'd probably test variations of this where you indicate the hassle of the existing solutions. The goal being to further separate your solution from theirs as being the "obviously" superior answer.

Hope this helps.