It's not at all that Henry Halfhead is bad. It's good enough fun for the two hour runtime it offers. But it feels like the sort of game you'd play for 15 minutes, say 'wow, this will never get old!' and then 45 minutes later you're kind of thinking maybe you were wrong. If it committed more to being silly than to reminding you how fun silliness is by taking it away, then it would get old a lot slower, and would likely sustain itself for said two hours. Unfortunately, like Henry himself, it gets old a bit too fast to leave much of an impression.