I believe Kevin Hart is as funny as Chevy Chase was and I think he will have a decent career over the next decade. I do not believe he has the same style as Chevy Chase and I have a difficult time comparing the two, but Hart definitely knows what he's doing when it comes to comedy.
The problem with comparing one comedian to another in something as subjective as funny is that it changes determining on the person you ask. I'm not a fan of Kevin Hart or Chevy Chase, but I understand that Chevy Chase has given great things to our comedic culture. We should respect that.
While Kevin Hart is an entertaining comedian in his own right, it's impossible to compare him to any of the great comic actors of the 80's. Chevy Chase and similar comedians of their time had something unique that is hard to come close to. Maybe there are people out there who disagree, but for me no one can reach the same level that Chevy Chase did.
I really do like Kevin Hart. To myself thou, he is no where near as funny for Chevy Chase. I find some of his humor to be off, and it just does not appeal to me. On the other hand, I love everything that Chevy Chase has ever played. He is more subtle with his humor.