Joe Danger 2 improves upon the first game by adding more vehicles and other ways of transportation. I don't know what to tell you about it really. If you played the first one this one is very similar. Yes, the different vehicles add more variety to the game, but it's still all about collecting stars, letters and other collectibles, while performing as many stunts as you can. Except this time, the whole game is set on a movie set. Even the graphics look the same, with just slightly more variation.
Also, the game performs much, much better than the first one. The first one had some annoying frame drops, but JD2 runs at a solid 60FPS at all times. But this Joe occasionally has some frustrating levels with not enough checkpoints.
In the end Joe Danger 2 still isn't very long if you don't like to collect stuff, but if you do you're in for a treat. It's a great game, just don't expect too much new stuff. However, if it's your first Joe you have nothing to worry about. Just enjoy the ride !