This is what I want in a comedy. Genuinely funny people in unexpected and refreshing situations. The film does an impressive job of balancing a large scale with a 'bottle episode' of characters forced together. And although there are a couple of standout performances (McBride, Cera) its tough to find any obvious faults with the entirety of the cast - and that goes for the film's insane amount of cameos as well.
This Is The End is a bizarro world where its lead actors (very) loosely play themselves, but the benefit is that doing so builds an anchor around which the epic scale of the film's events are grounded in our own (psuedo-)reality and amplifies the comedy in most situations. All in all, the film simply does a brilliant job of demonstrating that dick and shit jokes really can hold a big budget movie together.