Here is the definitive list. Let all debate cease.
PG--John Stockton. This one's a close call, but Stockton was the consummate floor general (all-time assists leader by far), a great defender (all-time steals leader as well I believe), and an extremely high percentage shooter on top of everything else.
SG--Michael Jordan. Best scorer ever, and not just because he took a lot of shots (very high shooting percentage as pointed out by others, and decent from 3-point range too), and a great defender.
SF--Larry Bird. LeBron is close, but Bird was, statistically, a better rebounder, defender, and shooter.
PF--I agree with everyone else that this is historically the weakest position, but the best option is without a doubt Tim Duncan. Extremely efficient, great in all facets of the game.
C--Shaq. I know there have been a lot of great centers, but people forget how unstoppable he was in his prime; there has never been player with his combination of size, strength, and explosiveness. Wilt was the greatest of his time, but he dominated against a league in which no one else had his physical tools, and I can't help but think Shaq would have been better than him had they played at the same time, if only because Shaq was/is so much bigger and stronger (320+ lbs. vs. 275 lbs.). And Wilt couldn't shoot free throws either.
http://www.basketball-reference.com/leaders/per_career.html