While many might think Apps are like lottery, i agree! Only if lottery can be won by hard work. Your App should be efficient, entertaining, original, well-designed, and well promoted! I provide 5/5 of that, and a lot more. In short, if you want a successful App me.
As for your logo You know Logos are like faces, once seen, everyone remembers them, unlike names. Although people would remember ugly faces faster, the really pretty ones are unforgettable. Mind you! plastic surgery ruins a face, whether it is pretty or not is told from the first look! :)