Who scored 20+ ppg from the early 2000's? I'll go from memory (no Googling) of guys that played from the 1999-2000 season through the 2005-2006 season then circle around and see who I got wrong.
How many of those guys could pull 20ppg with the defenses today? Look at those names you listed, many of those guys weren't even all stars, or were borderline once or twice all stars.
The game has changed, defenses are light years ahead of where they were years ago. That is why it is difficult to compare players 20 years apart, certainly when using raw stats.
No, it would NOT have been Durant vs. Bird with no help defense. Go watch some Youtube videos of games back then, especially in the playoffs. Good lord....
I do routinely watch older games, especially during the long dull summer months where there is no NBA to watch. I have over 100 games in my collection so I don't have to bother with hoping stuff is up on youtube.
There is a huge difference between the allowance of hard fouls/cheap shots back in the day and true help defense. The rules of the game at the time simply did not allow for sophisticated defenses and gave a player carte blanche to try and exploit a defender by himself.
If you are watching the Heat/Thunder game tonight, look at some of the early traps Durant is seeing. He is being doubled as far as 40 feet out, on occasion even without the ball. That simply would not have been legal in the 80s. The advantage an elite scorer has being able to pick their spots with impunity is huge.
http://www.youtube.com/watch?v=Rto2_oYVs0I
The "help" defense back in the day was different not only because you couldn't double without the ball, but also because when you leave your player to help out the rest of your team can't zone the remaining players. When you have 3 guys guarding 4 away from the ball but have to stick with a man defense you are in trouble. How many clips from this game do you see a double come to Bird, him just sit there and dribble in place as the double team has to cheat back to his player, giving him an ISO again? Do you see Melo or Durant just standing and watching a double disappear? Please.