I've never been a huge fan of Jim Carrey's goofier work (Ace Ventura, Dumb and Dumber, Cable Guy). When his character is too wacky, he tends to do too much and I lose patience with the whole shtick. But when he's forced to inhabit a more conventional identity, and reins in his wilder instincts, he's actually something of a decent actor with the capacity for broad humor that's also warmly human (Liar, Liar and Yes Man come to mind). Perhaps the best example of this, and my favorite of his filmography, is Bruce Almighty.
First off, when you include Morgan Freeman as a sarcastic, weary deity, Jennifer Aniston as an appealing, sympathetic girlfriend and Steve Carrell as a smug jerk of a colleague, you're most of the way home to begin with. But Carrey's Bruce Nolan is a good guy, although he's tired of the back bench at work, and wants more out of life. He just wants to catch a break (because dating Jennifer Aniston apparently isn't miracle enough) and snag a gig at the anchor desk. When it doesn't happen, he goes off the rails a bit. God doesn't appreciate being blamed for Bruce's ill fortune, and punishes (teaches?) him by giving him a portion of his divine powers and obligations. Some fun scenes ensue as Bruce struggles to deal with his sudden godliness and then, being only human, abuses it in ways both subtle and overt. Things work out in the end, of course, and Bruce happily returns to his regular life with the perspective that we generally tend to get what we deserve.