Yeah, I was a bit too eager on the Sid>Bossy, but its close still and case could be made for either one.
I'd already rank Crosby ahead of Bossy (based solely on what he's actually accomplished - no future projections involved).
Regular season offence
We can't simply compare top three or top five finishes, because Gretzky (and his linemates) were such outliers. Instead, let's compare the players to the NHL's 10th-place scorer each year. Here`s how they stack up:
Bossy: +39%, +38%, +17%, +16%, +15%, +13%, +12%, +5%
Crosby: +32%, +27%, +26%, +19%, +17%, +15%, +14%, +10%, +10%
It`s close in terms of regular season offense. Bossy has the higher two-year peak, but Crosby has nine years playing at least 10% above the tenth-place scorer, Bossy only has seven. Over their best ten years, Bossy was 13% ahead of the 10th-place scorer on average, Crosby was 16% ahead. Yes, Bossy was a better goal-scorer, but in terms of overall offensive contributions, I`m going to call this virtually even.
Defense
I`d give Crosby a slight edge. Bossy was remarkably average defensively. He wasn`t the soft, one-dimensinal player he was sometimes portrated as, but he wasn`t nearly as good as his plus/minus would suggest. Crosby has been above average over the course of his career (he improved a lot over time, of course, but on balance that`s how I`d rank him).
Playoffs
This is pretty even. Both have a Conn Smythe, but Bossy was far more dominant the year he won his. Crosby`s Smythe was fairly weak by historical standards. Advantage Bossy.
Over the span of his career, Bossy was 3rd in playoff PPG (minimum 50 games - excluding Gretzky and his linemates to make it a fairer comparison). As of this moment (ie before Game 1 of the Stanley Cup finals is played), Crosby is in sole possession of first place. Advantage Crosby.
Bossy made it to the conference finals five times (all consecutive) and was a major part in all of them. Crosby also made the conference finals five times. He was poor in 2013 but was strong in all other years. Still, I`d give Bossy the edge here.
Overall Bossy scored 1.24 PPG in the playoffs, and Crosby scored 1.11. Bossy scored about 12% more in an era that featured something like 20% more offense. Advantage Crosby.
Bossy has finished 1st, 2nd, 2nd and 5th in playoff scoring. Crosby has finished 1st, 2nd, and will almost certainly finish in the top five again this year, even if he doesn't play another game. Still, Bossy gets the edge.
Bossy only led his team in scoring in the playoffs three times. Crosby has already done so four times. He also contributed a bigger share of his team`s offense (30.2% for Bossy, 35.8% for Crosby - through 2016 only). Advantage Crosby.
International play
Bossy played in three major international tournaments. In the 1979 Challenge Cup, he was dominant for the first four periods of the three-game match, then invisible the rest of the way as Canada was upset. In the 1981 Canada Cup, he led the tournament in goals, and was tied for second (behind Gretzky) in points. He was named to the tournament all-star team. In the 1984 Canada Cup, he was very good but not great.
I won't re-hash Crosby's international resume since I assume anyone reading this would be familiar with it. On balance they're pretty even.
Longevity
Bossy is one of the very few upper echelon players in history that Crosby has an advantage on in terms of longevity. Bossy had nine full seasons and one injury-shortened season (maybe eight and two, depending on how to categorise 1984). Crosby has eight full seasons and four shortened seasons. Overall Crosby has played exactly 30 more regular season games and, entering tonight`s game, 13 more playoff games. This is an advantage for Crosby, but it`s a small one.
Recognition as the best player in the league
It`s been close so far, but this is where Crosby decisively pulls away.
Crosby has won two Hart trophies. He was a finalist (top three) six times. Even if you remove Gretzky, Bossy only placed third or higher in Hart voting twice - 1981 and 1982. That`s a huge disparity, and, in my opinion, that ruins the argument that Bossy was the better player. The voters aren't always right, of course, but a 6-2 lead, after accounting for Gretzky, is too big to ignore.
Here`s another way of looking at it. During Bossy`s career, his linemate Bryan Trottier earned 178 adjusted Hart trophy votes (adjusted so that each year is worth the same) - second only to Gretzky. His teammate Denis Potvin, a defenseman, a position that`s traditionally short-changed when it comes to the Hart, earned 30 votes. Bossy only earned 28. A lot of fans don`t realize this today, but Bossy was probably only the third best player on his own team.
Over the course of his career, Crosby is far ahead of Malkin in Hart voting. Through the end of 2016, Crosby is behind only Ovechkin, but I strongly suspect that after the 2017 results are released, he`ll move into first place. He`s close to doubling Malkin`s voting record.
Not to over-simplify, but Crosby is at worst the second best player of this generation in terms of Hart trophy voting. Bossy was only the third best member of his team.
The only counter-argument is Bossy was named the best player at his position more often (five-time FAST, three-time SAST). But it's a narrow lead (assuming Crosby is the second-team all-star this year, which I think is highly likely, he'll be a four-time FAST, three-time SAST). A small edge for Bossy, but not enough to overcome Crosby's much bigger advantage with the more significant trophy.
Conclusion
This turned into a much longer post than I intended. Although it was close up until the end, I think Crosby has already surpassed Mike Bossy.