Billy Smith is one of the most overrated goalies in hockey history. He played a total of 680 regular season games, but his entire reputation comes from 93 playoff games played between 1980 and 1984. In that period, the New York Islanders reached the Stanley Cup Finals five years in a row, winning four times before finally losing to the Edmonton Oilers. This gave Smith a reputation as a "winner" and a "money goalie", and booked his place in the Hall of Fame.
But how much did the Islanders, a team good enough to win four Stanley Cups in a row, rely on their goaltender? Evidence suggests not very much. The Islanders were consistently one of the top scoring teams in the league. In 1981, they led the league in scoring. In 1982, they finished 2nd to Edmonton. After a down year in 1983 (15th), they finished 3rd in 1984. From 1981 to 1984, the Islanders averaged 4.4 goals per game. In the playoffs, they were even better, averaged 4.7 goals per game over their 4 Cup runs.
During their Cup winning playoff seasons, the Islanders were ridiculously dominant. They went 15-6 in 1980, 15-3 in 1981, 15-4 in 1982, and 15-5 in 1983. In those four years, they only faced elimination once, winning the decisive game 5 against the Penguins in 1982. They also only ever trailed in a series once, after dropping the opener against the Rangers that same playoff year (which they followed up by rattling off 12 wins in 13 games to bring home the Cup).
The Islanders also had an incredibly low percentage of one-goal games. Only 20 of 99 playoff games were decided by a single goal, and in those games the Islanders went 13-7. That seems pretty good, but it is actually much worse than their overall record of 72-27. The record was mostly fueled by the 1979-80 team, the weakest of the Stanley Cup winning squads. From 1981-85, the Islanders had only 13 games decided by one goal in a stretch of 78 playoff matches, winning 7 and losing 6, indicating that Smith didn't exactly steal the close ones. And over 80% of the time, he could have let in another goal without even changing the final result.
So, evidence suggests that the Islanders didn't need top flight goaltending, since their team was so powerful they would usually win anyway. That reflects on Smith's value, but he doesn't really address his actual level of performance, which is what we turn to next.
Most of the games Smith played were before save percentage was an official stat, so we will have to rely on the traditional stats for the most part. Back then, however, the Islanders tended to platoon goaltenders during the regular season, which allows for a good comparison.
Billy Smith was an Islander from when they entered the league as an expansion team in 1972-73 until his retirement in 1989. Over that period, he played mainly with three goalies: Chico Resch, Rollie Melanson, and Kelly Hrudey. All three significantly outplayed Billy Smith in the regular season, but for some reason Smith was given the playoff starts that enabled him to build his reputation as a winner.
Between 1975 and 1981, when Smith and Resch shared the load, Billy Smith had a lower GAA in a season only once. Only twice did he play more games than Resch, and only twice did he have a higher winning percentage. For the period, Resch recorded a 2.55 GAA and a .662 winning percentage, much better than Smith's 2.81 and .621. Resch also posted 25 shutouts to Smith's 15. Nevertheless, Smith played 30 playoff games, nearly as many as Resch's 34. In those games, Smith's GAA was 2.87, worse than Resch's 2.49, but his record was 16-11 while Resch's was only 17-17. Maybe this apparent run of luck by Smith was what started to earn him a reputation as a clutch performer. A couple of shaky games by Resch in 1980 opened the door for Smith, and he played in 20 of 21 games as the Islanders won their first Cup.
Resch was traded during the 1980-81 season, and Smith's new playing partner became the 21 year-old Rollie Melanson. Despite his youth, Melanson posted excellent numbers over the next 3 seasons, recording a cumulative .906 save percentage, better than Smith's .901, and also besting Smith in goals against average and winning percentage. Nevertheless, Smith got the starts come playoff time, and rode along with the Islanders juggernaut to Cup after Cup.
Smith was awarded the Conn Smythe trophy as playoff MVP in 1983. He played in 17 games that year, going 13-3 with a 2.68 GAA. The Islanders destroyed their opposition, scoring 4.7 goals per game, going 15-5 and never facing elimination. They only played in one game that was decided by a single goal, a game that they lost. Mike Bossy led the team in scoring with 17 goals in 19 games (exactly the same as his Conn Smythe peformance in 1982), Denis Potvin added 8 goals and 12 assists from the blue line, and Brent Sutter had an excellent playoffs with 10 goals and 21 points to finish 2nd on the team in scoring. Melanson played in 5 games and posted a lower GAA than Smith. Yet somehow, the voters decided that the MVP of this scoring machine was the goalie, Billy Smith.
Melanson was traded in 1984, as another top prospect, Kelly Hrudey, was waiting in the wings. Hrudey arrived at the tail end of the Islanders' run of dominance, and once again Smith was soundly outplayed by his teammate. Hrudey's save percentage between 1984 and 1989 was .889, Smith's was .879. Hrudey posted more shutouts, a lower GAA, and a better winning percentage. He also took over in the playoffs from Smith in 1985, and Smith rode the pine during the playoffs for the rest of his career.
Another career accomplishment of Smith's is that he has the honor of being the first goalie to be voted the Vezina winner, after the rules were changed in 1982 from automatically awarding the trophy to the goalie with the lowest goals against. That season, Pete Peeters and Philadelphia had off-years, and Montreal (the Jennings trophy winners) split their playing time among three different goalies, leaving the door wide open. Richard Brodeur in Vancouver was almost certainly the best goalie that year, posting a winning record and a 3.35 GAA for a 77 point Vancouver team that scored only 290 goals (4th worst in the league), playing in the same division as Gretzky's Oilers. Brodeur's backup Glen Hanlon, an NHL starter for most of his career, had a .389 winning percentage and a 3.95 GAA in 28 games behind the same defence. But Smith led the league in wins and GAA, and as it so often does, that managed to swung the vote his way.
In summary, Billy Smith had an unremarkable career. He was almost always the second best goalie on his team, and his regular season stats are not outstanding. His reputation is based entirely on his playoff performance, played entirely behind one of the greatest teams of all-time. The Islanders of the early '80s were a dominant offence and defence that won Stanley Cups virtually unchallenged. They weren't reliant on their goaltending at all - their wins came from their prolific offence, and most of the time Smith could have given up another goal or two and still got the W. If Resch, Melanson or Hrudey had been in net instead of Smith, it is completely reasonable to expect that the Islanders would have won all of their Cups. In addition, his Vezina and Conn Smythe trophies were both questionable choices and probably undeserved. Billy Smith is one of the best examples of how a team can make their goalie look good; he is in the Hall of Fame today more because of what Trottier, Bossy, Potvin, and the Sutters did than anything he did on his own.