I've been doing a bit of work lately looking at even-strength save percentages, since the evidence suggests that they do a better job of estimating team-independent performance than overall save percentages, which can be strongly influenced by special teams play and the number of special teams opportunities.
We have official even-strength performances available from NHL.com since 1998-99, and one of the things I have been tinkering with is estimating even-strength save percentages for prior years based on goalie overall save percentages and special team statistics like power plays against and power play goals against.
I compiled the even-strength numbers for the consensus top 5 goalies of the official save percentage era (Roy, Hasek, Brodeur, Belfour, Joseph), and filled them out by estimating their even-strength records for the remaining years of their careers. I'm still working on getting the best fit, so these numbers will be further refined, but I believe they give a good approximation. Once again, what many people see as a "Top 3 and Lesser 2" is more probably a "Top 2 and Lesser 3", perhaps even a "1-1-3" ranking:
Dominik Hasek: .935 even-strength sv%, .914 league average, +.021
Patrick Roy: .921 even-strength sv%, .906 league average, +.015
Martin Brodeur: .922 even-strength sv%, .916 league average, +.006
Curtis Joseph: .917 even-strength sv%, .911 league average, +.006
Ed Belfour: .916 even-strength sv%, .911 league average, +.005
I also thought it would be interesting to post a breakdown of seasons by "poor", "average", "good", and "great". I defined poor as a save percentage of below 99.5% of league average, an average season as from 99.5% - 100.5% of league average, good as 100.5% - 101.5% of league average, and great above 101.5% of league average. Here is how each goalie ended up doing in each season they faced at least 500 shots against:
Hasek: 0 bad, 0 average, 5 good, 8 great
Roy: 1 bad, 1 average, 6 good, 10 great
Brodeur: 0 bad, 7 average, 6 good, 2 great
Joseph: 3 bad, 7 average, 3 good, 3 great
Belfour: 3 bad, 6 average, 6 good, 2 great
There is a consistency argument that can be made for Brodeur over Belfour and Joseph, although some of the bad seasons for the latter two guys were late-career seasons when they were clearly on the decline. Belfour also had one average season effectively spiked by getting traded to the expansion-era San Jose Sharks, who were a legitimate shot quality outlier. In addition, Brodeur almost always tended to play more minutes than the other guys did, so as such we would expect his numbers to less affected by random variations.
If we further restrict it to seasons where the goalies faced at least 1000 shots against, and were between the ages of 21 and 36 (to match Brodeur's career so far), we get the following:
That shows much less of a difference between the bottom three guys, particularly for Joseph who really had his game desert him in his later years.
I still find it hard to see a significant difference between Brodeur and Belfour. There's not much between them other than in the games played column, and one could argue that Belfour closes some of that gap with superior playoff results. Over a 20 year career Brodeur likely gives a team more total value, but if you had to choose one of them to play a key game for you it's pretty much a tossup.
There was also probably little to no difference between Brodeur and Joseph in terms of stopping the puck, once you put the two of them on a level playing field. Joseph didn't age gracefully, but at his peak he was probably better than Brodeur at making the first save. When taking everything into consideration, however, Brodeur has much better non-save skills and that breaks the tie.
In an all-time perspective, if one was to rate goalies based on how they actually played, not based on how well their teams did or how good sportswriters thought they were, then Brodeur should be ranked much closer to Belfour and Joseph than to Hasek or Roy. As I've said many times before, I believe it's a mistake to rank Brodeur up with the latter two, as both of them had 6-7 years of prime seasons at a level well above anything Brodeur ever reached.
I hope to post some more numbers for other goalies when I get a chance. I did manage to run the numbers for Roberto Luongo, since he has done well in similar performance measures. I know it doesn't matter anymore now that he let in 7 goals in one playoff game, thereby rendering all previous results obsolete, but Luongo has a career .929 even-strength save percentage, compared to a league average of .918, for a +.011 difference, with 5 good seasons and 3 great seasons. That puts him on a trajectory to end up somewhere around the Belfour/Brodeur/Joseph range or even a bit above, keeping in mind that Belfour and Brodeur close the gap some when you factor in their apparent shot prevention effects.