They called Shaq one of the 50 greatest players after his 2nd season.
Look at the numbers LeBron is putting up, he could retire today and still be in the Hall Of Fame. By the time his career is all said and done he may be the all time leader in Points, and be high up in the ranks of assists, and rebounds. He is a great leader.
And about him retireing today, he hasn't won a championship, hasn't won an MVP award, and just because he is a great leader doesn't mean he is HOF worthy.
Charles Barkley, John Stockton, and Karl Malone never won a championship
And with the MVP argument, I'm not sure what you're talking about. Many great players never won an MVP. Besides, he'll get his MVP and Championship this year.