The Celtics are known for playing long, worn down series. All of their playoff victories, in the 2008 playoffs, came in 6 or 7 games; the fact that the Bulls almost won the series is not surprising.
I think the Celtics might have beaten the Magic, even without Garnett, had Paul Pierce played better, in game 7, and had Doc Rivers used Mikki Moore, instead of playing a four guard alignment which ultimately allowed the Magic to score at the basket at will.
Oh, well. The Magic won. Good luck to them. They played hard to get where they are now.