There are quite a few games like this and this is one of the better out of them.
Even though I say this there are a few areas which I think could be improved on:
Difficulty: too easy and went through the game too quickly.
Story line: uhm I suppose you could add one??
Music: It's okay and does pass for the standard of this game but it can be improved on.
Graphics: nothing that really grabs my attention but with the other games that are like this it shows to be average.
Length: add some more levels or just improve the difficulty.
Some things that I liked about this game were passing the grenades (I believe you could do alot more with this though) and the pirates... I love pirates okay just something personal i guess...
Here is my main suggestion: add some flashy cut scenes. not too sure if it would go well but would be a good test just to see how people act to it.
All in all an average game and thank you all who read this.