The film borrows a lot from the seminal classic "It's a Wonderful Life", including a cute homage in which Bruce literally lassos the moon to make the night more romantic.
It's just that, given the rich premise of the film, writers Steve Koren, Mark O'Keefe and Steve Oedekerk could have done much more than turn it into a weak copy of "It's a Wonderful Life."
Basically, Bruce Almighty wants to be It's A Wonderful Life (explicitly referenced twice in the film) meets Groundhog Day, except they only really got as far as the pitch ("Jim Carrey IS God!
Considering that the basic story is just a variation of the old "It's A Wonderful Life" plot, it isn't surprising that the protagonist eventually recognizes that theme and has a transformation for the better.
An "It's a Wonderful Life" of 1946 -- which it seems to have as a model -- it's not.
Try to envision -- if you dare -- Frank Capra's It's a Wonderful Life with boob jokes, a running gag involving a urinating dog, a "butt monkey" and, worst of all, a tendency to mock the sort of gooey, uplifting twaddle that Carrey's film finally becomes.