I go a bit differently, I guess.
1) Panarin '18-'19 -> franchise record for points and really was the driver of that offense for much of the season, and could have had even more points if the power play wasn't horrendous
2) Bobrovsky '12-'13 -> yes, it was fewer games, but he put that team on his back. He started the final 13 games (going 10-3) and 23 of the final 24 (going 18-5-3). I picked it over '16-'17 because it was carrying a worse team and also it was his first season here, so you'd figure there would be have been a "newness" factor that might have slowed him down.
3) Nash '08-'09 -> to me, it was a more complete season from him than his Rocket Richard season and he helped carry a mediocre team to the playoffs as a two-way captain.
4) Whitney '02-'03 -> nearly a point per game wizard on a horrendous team (24-52-76 in 81 games).
5) Bobrovsky '16-'17 -> a .931 save % while starting more than 3/4 of the team's games is absurd; it's also the single-season franchise record for goalie point share, with an absurd 33.5 GSAA.
Honorable mentions (no particular order):
-Bobrovsky '18-'19 -> a season remembered more for the breakup (and tantrum), Bob pitched 9 shutouts and also exorcised some playoff demons.
-Mason '08-'09 -> for me, just too inconsistent to make it into the top 5 (10 shutouts, yes, but also wasn't even in the top 5 in the league in save %)
-Sanderson '02-'03 (and also first 30 goalie season in '00-'01) -> a 30+ goal scorer on a really bad team, he was one of the few entertaining offensive players in the early days of the franchise
-Atkinson '18-'19 -> for me, carried a bit by Panarin that season, but 40 goals is no fluke (well, for Cam it maybe was as he only has one other 30 goal season in his career)
-Tugnutt '00-'01 -> a near-.500 record with a .917 save % in a pretty terrible inaugural season
-Denis '02-'04 combo -> 77 games played in '02'-03 (a record that will never be broken, imo) followed up with a .918 save % season in '03-'04
-Werenski '19-'20 -> was leading the league in goals by a defenseman when the season shut down, he's still never topped 20 goals in any other season and finished 8th in Norris voting
-Jones '17-'18 -> his best and most complete season here, finished 5th in the Norris
-Panarin '17-'18 -> just a dynamo in his 1st year, came in 14th in Hart voting
-Nash '03-'04 -> the Rocket Richard season
-Nash '05-'06 & '07-'08 -> Nash finished with 54 points in 54 games played in '05-'06 and put up 38-31-69 in '07-'08, probably his 3rd & 4th best seasons here on some floundering teams
-Foligno '14-'15 -> a career year that he's never come close to replicating, he and Johansen were about the only thing working offensively for most of that season