I'd say the game is okay. There's not a whole lot of challenge to it when you consider that there is no time limit so you can take as much time as you want to shoot (I find it very easy to hit the birds as soon as they appear since they always go straight up before moving around randomly). However, once the birds get passed the first few second, their sporadic makes it tough to hit them. I have never played a full official game of Duck Hunter so I don't know how it worked originally, but only letting two birds out at a time gets boring. Also, a small set of instructions would be nice (explaining things like how many birds you have to hit to make it to the next round).
Still, no bugs and (although I haven't played "Flappy Bird" and have no reason to hate it other than the fact it is an extremely simple game that just happened to become more popular than the thousands of games that were made just like it years ago) I'd say your game is good at representing people's distain for the game. Good job and I hope to see more from you.