I think there were more deserving candidates. But I want to compare him to other relief pitchers since it seems like the voters wanted to put another one in there.
A problem, though is that the use relief pitching evolved before, during and after Sutter's career. He many not be comparable to relievers outside of his era. He came before the era of "closers," the one inning type of reliever. He was probably used more late and short than guys before him.
He had 5 seasons with 100+ IP and 5 more with 80+. From 1989 (the year after he retired) to 2002 not one of the top 25 save seasons had 90+ IP. Only 8 had 80+. When Sutter saved 45 in 1984, he pitched 122 innings.
So I compared him to the relievers of his own time. I found the top 25 in saves from 1976-1988 and then eliminated anyone with under 500 IP. That left 22 pitchers. How did he do compared to those guys?
First, RSAA per IP. RSAA is "Runs saved against average. It's the amount of runs that a pitcher saved vs. what an average pitcher would have allowed." It is from Lee Sinin's SABERMETRIC BASEBALL ENCYCLOPEDIA. It is park adjusted.
Here are the top 5
Dan Quisenberry .153
Lee Smith .123
Goose Gossage .12
Bruce Sutter .118
Kent Tekulve .114
Sutter is far behind the leader, Dan Quisenberry. Dan Quisenberry actually had more RSAA while pitching fewer innings (1,042 vs. 958). Gossage had more IP than Sutter (1,217) in this period. And Tekulve pitched 1,319 innings and is just barely behind Sutter. So Sutter hardly dominates here. Dan Quisenberry finished at .142 for his career in 1,043 IP). Tekulve finished his career at .104.
Now strikeout-to-walk ratio . I included HBP here but did not count IBBs. Sutter was 2nd here at 3.6. Quisenberry was first at 3.66.
In HRs per IP, Sutter was only 16th at .074 while the average for the group was .069. He did pitch more innings in Wrigley Field than in St. Louis. And he also pitched in Atlanta, a good HR park. But in St. Louis his HR per IP was .076, actually just a bit higher than overall.
This is all a little unfair to Sutter. I am using his whole career while for the other guys it may only be a part of it which misses their decline phase, raising there averages.
Sutter does have 3 of the top 6 seasons in RSAA per IP for pitchers who are in the top 50 seasons in saves from 1976-88. No other pitcher has more than 1 season in the top 13.
Bruce Sutter 1977 .354
Dan Quisenberry 1983 .252
Donnie Moore 1985 .247
John Franco 1988 .232
Bruce Sutter 1979 .227
Bruce Sutter 1984 .22
Sutter led the league in saves 5 times and had 3 other top 5 finishes. That is the kind of stat we expect from Hall of Famers. Is that enough to get in? Hard to tell.
He had 27 more career saves than the next closest guy over his career. The leader from 1990-2002, Wetteland had just 18 more. Sutter was 62 ahead of 3rd place. Wetteland is only 36 ahead of 3rd place. Of couse, Sutter may have specialized in "saving games" more than was normal in his time and he may have been an early closer. Where as today, there are so many closers it is hard to dominate.
I also created a point system where a pitcher gets points for where he ranks each season in saves. Coming in first gets 10 points, 2nd 9, 3rd, 8 etc. Ties get half points, like a tie for first gets 9.5.
In the late 80's pitchers started getting more saves because the "closer" speciality developed. 19 of the top 20 seasons have come since 1990. Only 6 of the top 50 came before 1990. This is due to changes in the save rule and the development of the closer. So with this point system it puts relievers in the past on a more equal footing as current relievers.
I looked at all years since 1950. I eliminated any save totals less than 10. Then I compiled the points each guy got for his whole career. If a guy had a 1st, a 2nd and a 3rd, he gets 27 points. Here are the top 10.
Lee Smith 107
Fingers 100.5
Gossage 79
Hoffman 79
Face 78.5
Sutter 77.5
Franco 75.5
Eckersley 73
Wilhelm 69.5
Rivera 69.5
We might wonder how Sutter gets in before Smith, Gossage, and Face. Smith's career RSAA per IP is .111. Gossage is .088. Face is only .033. We could say Sutter is ahead of Gossage and Face by enough to be go in before them. But Smith, with 478 saves and more points on this rank scale, could be seen as more deserving. Smith led the league 4 times, was 2nd 4 times, had 3 other top 5 ranks and 3 other top 10 ranks. Pretty impressive.