Think alot of people fail to realise just how touch and go Utd's treble was. Bergkamp missed a pen that would have sorted the Cup and we missed out on the last day of the season for the title whilst everyone knows about how flukey Bayern was. By no means did Utd sweep all before them.
Tbh the Arsenal 1999 side was just as good if not better. World class back 5 then Vieira, Bergkamp + the likes of Overmars/Anelka who soon left for Barca/Real for a combined £50m(a huge huge sum at that time actually).
That's not to take away from the achievement, just judging the quality of that side with clear eyes. Utd 2008 were Fergie's best ever and arguably the overall best imo.