Dane Cook is just not funny, at least he isn't funny here. I think he has some potential. He was fine in Mr. Brooks, and he looks to be fine in Dan in Real Life. As a leading man, well, let's just say that he isn't ready for it. He is betrayed by a weak script that mistakes crassness for comedy and fails to inject any heart. On the plus side, Jessica Alba looks more at home here than she did in Fantastic Four, but that may have more to do with the lack of blonde hair and blue eyes here. Completing the troika is Dan Fogler who handled himself well as the comedic sidekick. He has some of the more humorous lines, and comes out mostly unscathed.
Bottom line. This is not an awful movie, but it is really not all that good. The high concept was not well thought out, the script has no substance, and the lead performance is flat and humorless. I think that about sums it up. Alba is fine, she is not the best actress but she always looks good. This fails to live up to the high bar set by R-rated comedies earlier this year (Knocked Up and Superbad).