You really need a good dedicated macro lens to get a great photo of a butterfly (take a look in the main butterfly gallery and you will see what I mean). The other problem you have here is the bright patch of sunlight which has fallen on the butterflys head washing out the detail. Not really anything you could have done about that though. You seem to have gotten the focus area right and the DOF is quite good. I would have done some post processing to bring out the color a bit more and probably cropped out a fair bit of the unnecessary background (not a problem to do here as it is a relatively large res photo).
The best way to learn, though, is to just keep taking photos, the more you do it the better you will get and the higher your own expectations will become.
I prefer to use a 200mm lens for Butterfly photos, then you don't have to get so close and scare them away. And you don't need to do much cropping at all. I agree with Samatars comment.
I'd truly love to know what you think. Thanks!