Its a start.
I'd give you a higher rating if there was more to it. I see that the side-scrolling and the movement of left and right is working okay, but other than that there's really nothing to be said about this other than that. There's no sprite animation, decent start though.
When you do make your next game make sure its complete, not everyone goes to Newgrounds to test games they also want to play it. You'll get positive feedback on how finished the game is.
When you make a game, keep in mind of the important stuff like sound effects, music, background and foreground, gameplay functions, and so forth. Take all this, apply it to your next game project, and take as much time as you need. A game doesn't have to be long to be a good one. See if you can make a game with a few stages and perhaps a small story to tie in for theming to make the game alittle more involving if you like. I would really like to see your version of a short finished game of Metroid. If there was something of an exploration game like Metroid in NG I would totally come back and play it many times over.
I hope this review helps you on your next project. Good luck.