These are questions asked by those with no real sense of history.
My top 5 would read as follows:
1. Wilt Chamberlin
2. Michael Jordon
3. Bill Russell
4. LeBron James
5. Kareem Abdul-Jabbar
I have 100% confidence that you will 100% disagree with my rankings, and that's OK. You probably also disagree with Peter King's atrocious pre-season power rankings. The difference is my rankings are, to some extent, well thought out (and I can justify them with numbers) while King's rankings are an attempt by SI's football transcriber to generate page views.
My point is this. Both Jordan and LeBron are undeniably great players. Once you get into the top 5 of all time you're dealing with the complicating factors of position, era, and supporting cast. This is doubly true when you bring in the red-herring that is championships.
While I do believe that championships play a role in determining a player's overall greatness it's not as big of a role as other factors. This is doubly true when you are discussing team sports. Is there any doubt that the Celtics would have won all of the championships they did had Chamberlin been their center over Russell? Had LeBron the supporting cast (and coaching) that Jordon enjoyed do you not think he would be sniffing 5 (or six) championships at this point?
For me, Wilt Chamberlin is clearly the best NBA player ever. What he did in terms of points scored and changing the game is unrivalled. Jordon is a clear second for the same reasons. Bill Russell is 3rd in my opinion not only based on the fact that he won it all 11 times, but he was also a five-time League MVP and was the dominating defensive force of his time. LeBron is currently at 4, but could move up if he continues at his current pace. The one that I struggle with is Abdul-Jabbar. He was undoubtedly a great center who played on some great Lakers teams. He surpassed Chamberlin as a point-scorer but I never felt like he fundamentally changed the game. He also had the honor of playing with the number 6 player on my list, Ervin "Magic" Johnson.
So, after the top 5, my bottom five looks like this:
6. Ervin "Magic" Johnson
7. Hakeem Olajuwon
8. Larry Bird
9. Moses Malone
10. George Mikan
Your mileage may vary.