Pitch Perfect is a great example of this. It's biggest star name is Anna Kendrick, which has been great in a lot of supporting roles in a lot of good movies (recently End of Watch) but isn't necessarily a good fit for playing a first-year college student. The story revolves around the collegiate Acapella music scene, and is setup as the usual "bunch of misfits overcome the odds" storyline. It's felt as if it was trying build of the success of Bridesmaids in having a mostly female cast combined with gags about sex and vomit. It looks, on paper, pretty derivative, and it makes me wonder why I rented it in the first place.
But it turns out that Pitch Perfect is both very funny and extremely charming. Yes, all the actors are way to old for college students but you forget this pretty quickly as all the main cast are well drawn and interesting. Crucially, there are no "villians" in this story; rivals, sure, and internal disputes, but its not a story where victory for one requires destruction of another, and it's not until you think about it that you realise how rare that is in most movies. It turns out you can talk (or sing) out your differences in a film that isn't some artificially worth Oscar-bait piece.
Its also careful not to laugh at its subject matter. Acapella Singing may be a little kooky as a competitive field, but its never the butt of the joke here. In fact, it's treat pretty warmly, and the setpiece songs - most notably a couple of song-battles about half-way through - give the film pizzazz and energy. And it's just funny; steadily, solidly, funny and whilst I don't recall a number of big, fall-off-the-sofa laughs I smiled throughout and it left with that warm, amused glow at the end. And the more I think about it, the more I think that's been pretty rare for comedies over the last few years, and maybe its worth watching just for that alone!