I agree with many of you that the 2000-01 team was indeed overall better than 99-00 team. I remember going into almost every game that season sort of expecting at least 4 goals to be scored. I can't remember a time since that has happened though 08-09, 11-12 and last season were somewhat in the ballpark.
There were many factors why the Devils lost in the finals that year, but the biggest ones were in no particular order:
1) Marty being bad. He had a shaky regular season as well but was propped by the fact that the Devils were an offensive juggernaut and could score 4 or 5 goals when the other team scored 3-4 on Marty.
2) Injuries. I remember McKay getting hurt and I think a few other key guys were playing a little wobbly by that time too. Also, keep in mind, the Devils did play a ton of hockey between the previous season and this season as well so fatigue was showing.
3) Mogilny disappearing after the second round. He did this in the previous postseason but this was more pronounced in the drop off. First 2 rounds: 13GP, 4G 8A 12P. Last 2 rounds: 12GP, 1G 3A 4P.
4) Devils getting cocky. I remember going to game 6 in 2001 and seeing the limos lines up outside for the Devils players. From what I have heard several times over the years, they were even setting up the locker stalls with protective screens for the champagne before the game even started.