According to the Bleacher Report, it's the Lakers.
After comparing each team's all-time best players (at their peak), position by position, and doing the same with the coaches, the site gave the Lakers a 4-2 advantage.
The Lakers edge the Celtics at center ("Shaq playing at his peak level would be the most dominant force. Boston would have no one that could effectively stop him one-on-one"), shooting guard ("Behind Michael Jordan, Kobe Bryant and Jerry West are the best shooting guards in the league's history"), point guard ("A great aspect of the Lakers' backcourt is its versatility. Besides Goodrich and Magic, Kobe and West would be perfectly adept at running the point") and coach ("While Auerbach is one of the greatest coaches in NBA history, Phil Jackson is arguably the best. ... Perhaps right behind Jackson and Auerbach in the annals of NBA coaching greats is Pat Riley.").
Boston gets the edge at power forward ("The power forward position is one of the weaker areas on the all-time Lakers team. By default, Pau Gasol is the best pure power forward in the team's history") and small forward ("Although the talent on the Lakers' side is impressive, Boston has a better counter punch. Larry Bird may be the best premier shooter in NBA history. ... Paul Pierce is another excellent all-around player for the Celtics").
Just some interesting summer reading ...
-- Chuck Schilken