I have to disagree with you on the talent claim. You have to have certain talents to be a successful actor/entertainer, otherwise everyone would be one.
Just like you have to have certain talents to be an athlete.
I know its not fair to say they have no talent but acting is something that can be taught to a degree and you don't even have to be that good at it to be quite successful. Jerry Seinfeld for instance. Whereas to make it to the professional level in sports you have to be truly gifted.
Athletes entertain. Celebrities entertain. Nothing more and nothing less. I always get a laugh from the guys who think their unhealthy obsession over sports is somehow different than females doing the same over the Hollywood elite.
Not much difference in the realm of entertainment between the two but sports fans passion is more for the sport itself rather than the individuals who play them imo. I agree with you that some people do have what you call an unhealthy obsession. Sure, root for your team but at some point you have to realize its just a game and you need to know whats really important in life.