The first 20 minutes are really funny, but that's it?

Rating: Null/10 (12 December 2015)

You know, I knew this wouldn't really be my type of humour, but when I saw how hilarious the first 20 minutes were, I knew it might be my type of humour. The rest of the movie became less funny and more boring as it went on. How could humour understandable enough for teenagers and meant for adults get worse? It became less funny and less frequent.
The concept was rather intriguing, but it's not going to matter when it gets stale and boring after a while.
Pros:

Funny first 20 minutes

Unusual concept

Cons:

Just uninteresting after that

Rating: 4+. I know I haven't really watched Family Guy, but I found almost all clips boring.