Ok, to begin, I'm a Cubs fan, Lee Smith was my first favorite Cubs player so I can't say that I'm very objective on this topic, but I wanted to make sure I looked at the numbers closely to convince myself that Smith really does compare very well to current Hall of Famer's.
Looking at relief pitchers either already in the Hall of Fame, that pitched in a similar timeframe (1970's to current) or pitchers that will likely enter the Hall soon after they get on the ballot, I chose the following pitchers to compare with Lee Smith's accomplishments: Rollie Fingers, Rich Gossage, Bruce Sutter & Trevor Hoffman.
How many times were each reliever an all-star?
Lifetime ERA and ERA+ (sorted by best ERA+)
Total Saves, Save percentage (saves/save opportunities) and all-time rank
So, as you can see, Lee Smith matches up very closely to current Hall of Famer's. One of the more interesting parts about comparing Lee Smith to relief pitcher's both in the era before and after him is the difference between how relief pitchers today are generally expected to pitch just the ninth inning where as in year's past (that Fingers, Gossage and Sutter pitched in), relief pitchers often pitched multiple innings to earn a save. The difference in save percentage really shows up with this so I did take a look at both his percentage when he entered the era where relief pitchers generally just pitched an inning and also looked at the list of the leaders in number of saves over an inning. Here are those results.
The top 4 relief pitchers for saves where the pitcher pitched more than one inning isn't a surprise. Lee Smith is 4th behind Fingers, Gossage and Sutter and all are very close.
Breaking down Lee Smith's save percentage in the 2 different era's was done in this way.
In 1980, over 60% of all MLB saves were over an inning. By 1990, that percentage had dropped to 30%. When reviewing Lee Smith's statistics, his innings pitched versus number of games came close to 1 inning per appearance in 1991. Smith pitched from 1991 to 1997 and had some of his best seasons in the early 1990's. His save percentage pre-1991 is 80.3%, still better than Fingers, Gossage & Sutter and post-1991 his percentage improved to 84.9% despite his last 2 years being the worst of his career (discarding these 2 years, leaves his post-1991 percentage to 86.9%). His save percentage is lower than that of Trevor Hoffman's 88.8%, but it is certainly still comparable to the Padres great reliever who is certainly a strong contender for the Hall when he is eligible (5 years after retirement).
Doing this comparison certainly convinced me that Lee Smith is just as good as Rollie Fingers, Goose Gossage and Bruce Sutter, however there are 3 arguments that current voters for the Hall of Fame would likely use against his election: