So-so
Alright so I'm a fan of Ben 10 which is why I played this game and it was a huge disappointment.
First, perhaps a bit more research would help. You're playing as Ben from Alien Force yet when you click to play it shows a picture of young Gwen. Granted, Kevin is a bad guy but in the second series he's on their side so there seems to be a bit of a continuity error there.
But people who haven't seen show probably won't notice care. However, there isn't any good game play to back it up. Ben shoots stuff? With what? Ben's power is to change into different aliens. I know that may be too advanced for a simple flash game but given the ability he has to shift it could have opened up a TON of game play options. However, it's just jump and shoot. Enemies are few and far between and show little variety. Granted, I stopped playing at the second level but that's because I got BORED!
I played this hoping to see some alien shifting but kicking action but I just got a mediocre platformer.