If you go expecting to see a gut-busting laugh-out-loud comedy like the usual Jim Carrey-Tom Shayac production, you'll be disappointed. (But it also doesn't have the bathroom humor -- a relief to me.)
But INSTEAD I suggest you think back to those great religious epics of the 1950s -- but with many light-hearted moments (instead of the heavy melodrama those movies had). I think then you can just sit back and enjoy this movie.
Steve Carell is a master of subtle comedy -- the comedy of character nuances. He's not a big broad over-the-top comedy actor like Jim Carrey. So it's not really fair to compare him to Jim and the Ace Ventura movies.
It must be a lot of pressure on him: "You're the star of the most expensive comedy ever made! Talk out of your butt or something!"
They have him doing some slapstick while clumsily building the ark, but it isn't really funny. The film is stocked with expert comedy actors, but only Wanda Sykes got any laughs out of the audience. (But then, it's said Wanda Sykes can get laughs just reading a phone book.)
Sadly John Goodman is wasted as "the heavy". Over the closing credits, you see a moment of him comic dancing and you remember how funny this guy is.)
So if you turn off your laugh-o-meter expectations and just look at it as a sweet story of faith with a few smiles and a lot of delightful animals and some great disaster effects, you'll enjoy it.