If the first Kick-Ass movie was that cool cousin, who's a bit rough around the edges and definitely a badass, then this film is that young brat, who tries to imitate said cousin, but only partly succeeds.
The first Kick-Ass film had a few good things going for it. It had a completely new take on the superhero genre, it skillfully juggled both effective comedy and brutally violent action scenes, plus it had some pretty convincing characters and a dark storyline. The sequel, on the other hand, fails at the juggling part. The action scenes are still pretty brutal and effective, but the humour lacks that razor sharp edge that made the first one so believable despite its premise. Instead it relies on racial stereotypes and potty humour, which just isn't that funny.
Add in a lackluster storyline that honestly feels like watching tennis. First one character has a change of heart, then few minutes later he/she bounces back and another character decides to change his/her opinion, immediately after which the first one changes his/her stand. Rinse and repeat. A compelling and captivating story this does not make, especially when the villain generates mostly embarrassed facepalms and the final battle rejuvenates some of the first clichés the first film so artfully dodged.
That being said, the production values are still excellent, some of the new characters are pretty interesting (though there's way too many of them), I still like both Kick-Ass (Aaron Taylor-Johnson) and Hit-Girl (Chloë Grace Moretz) and they had some really good scenes together. If you liked the first film and want to see the storyline continued, this one is worth checking out if you're not expecting miracles.