Nicklas Backstrom is an elite player and Max Pacioretty is an elite goal scorer. We can lower him down to "great" to fit the argument but that fact remains. There are almost no goal scorers like him in the league.
Nicklas Backstrom got his 86 points playing alongside Alex Ovechkin and TJ Oshie the majority of the time.
Max Pacioretty scored his 35 goals and 67 points alongside Philip Danault (and Radulov) the majority of the time.
Backstrom 86 points
Ovechkin 69 points
Oshie 56 in 68 games (or 67.5 points in full season)
Pacioretty 67 points
Danault 40 points in 82 games
Radulov
Radulov 54 points
Washington Capitals
263 Goals For
86/263=32.7%
Backstrom was part of 32.7% of Washington's scoring
Montreal Canadiens
226 Goals For
67 points/226=29.6%
Pacioretty was part of 29.6% of Montreal's scoring
The point is that while Backstrom is elite himself, clearly outshining his teammates, he's had a lot more to work with that Pacioretty. There's no doubt in my mind that Paciorettt's numbers were deflated due to playing with Danault, just a like Backstrom's numbers were helped by having such elite talent surrounding him. Backstrom on the Habs ends last season with ~73 points.
What we should be doing is solving that center problem by finding someone to support Pacioretty. Trading Pacioretty for Backstrom straight up is indeed defensible but it still leaves us with quite a void.
Also, I'm not convinced that we haven't lost the trade if we include two first round picks and I'm often someone who's "meh" about picks in a trade for talent.