Like the previous poster, I am a long time fan with memories going back as far as 1958. Attended many games in the old MSG and was a season ticket holder during the first decade at the current MSG.
It is difficult, if not impossible, to compare teams from different eras. If you subscribe to the idea, as I do, that athletes are continually becoming better (bigger, stronger, faster, etc), than the teams from the early 90s would have beaten the teams from the early 70s. Though it might be heresy, I honestly believe that a bottom level team from today would easily beat, say the great Montreal teams from the 50s, eight games out of ten. Not only are today's players bigger, stronger, and faster, but they are more skilled.
So, I think you need to remove the evolving skill level of players from the equation and just look at teams in relation to their relative eras. The 91-92 teams was a wonderful team and I was really upset when they were eliminated. That is when I really began to take seriously the idea that I would live my entire life without seeing the Rangers win the Cup. If the question is which team did I feel had a better chance of winning the Cup as the playoffs started, 72 or 92, I would have said 92. At the start of the playoffs in 72, I really had little confidence that we were going to win the Cup. The Orr/Esposito team was at its peak and Ratelle was hurt.
But that is not the question. The question is which is the best Ranger team not to win the Cup. I would have to say 71-72 team. That was a team that had been building for years and was at the peak of its talent level. Looking at our current team, we are always complaining about the lack of depth we have and our inability to ice a legit. 3rd line. The 71-72 team was so stacked that its 3rd line was Pete Stemkowski, Ted Irvine, and Bruce MacGregor: all skilled players with the ability to play higher up in the lineup. The team was stacked.
The unanswered question of course, is whether that team could have won with a healthy Ratelle. To this day, I can still see Dale Rolfe taking a shot from the left point and the puck hitting Ratelle in the ankle. The silence in the Garden when he limped off the ice was "deafening." Who knows.....
I have a soft spot for 91-92 with Messier and the emerging Leetch, Richter, Graves group that would win two years later. I have little doubt that the 91-92 Rangers could have defeated the 71-72 Rangers. But taking into consideration only the time frame the teams played in, I believe the 71-72 team is the best Ranger team not to have won the Cup.