Well, many people do not find Kevin Hart funny at all. This is primarily because most of the stand-up comedy that he does involves humor that is derived from his experiences as a black male with a very large extended family. This is a situation that which not all of us can relate to or have experienced.
Hence, only a specific fraction of the people find Kevin Hart to be extremely funny and these are the people who can actually relate to all that he is saying. While to us, it usually does not make enough of a sense at all.