Young, stat-crazy NBA fans don't know how good they have it. Just to throw an NBA old-man anecdote out there: I got my first idea for a player rating measurement when I was about 13 years old. In order to obtain the data to calculate it, I had to write to the league office and beg for a packet of statistics. (Which they sent!)
That old formula of mine has been lost to the dusts of time, but I still love to rate players as much as ever. So it was great pleasure that I participated in ESPN's process of ranking the best players of all-time. Because of the incompleteness of the historical statistical record, we had to rely as much on memories and stories as hard data when slotting in anyone who came before Magic Johnson and Larry Bird, though we have methods for gleaning quite a bit statistically from the little bits we have left behind.
As it happens, the history of roto sports -- or fantasy leagues, in the modern parlance -- is roughly the same age as our history of (mostly) complete NBA statistics. We plumbed that record a few weeks back to look at where Kobe Bryant rated in his career as a fantasy asset. In that vein, and borrowing the same methodology, let's get into the spirit of #NBARank and look at the best-ever single-season fantasy performers.
The methodology is spelled out in the link, but the long and short of it is that I've adapted ESPN Fantasy's Player Rater formula and incorporated turnovers, because I think they should be there. I'm including this year's results in the rankings. And to avoid redundancy, I'm only allowing each player to appear once, with his best fantasy season, so we don't end up with a long list of Michael Jordan campaigns.
As mentioned, these ratings encompass the 3-point era, beginning with the 1979-80 season. (Note: The NBA, of course, denotes each season with its two years separated by a dash; here I'm just listing the second year.)

1. Michael Jordan
Position: SG
Year: 1990
Player Rater: 15.63
Jordan's best fantasy season falls a year before his first NBA title. In the 1989-90 season -- his first under new Bulls coach Phil Jackson -- Jordan had the best 3-point shooting season that'd he'd have before his first retirement. At the time, 3-pointers still had a lot of marginal value so that would have made MJ an even hotter fantasy commodity than normal.
Just who would not have drafted him first in any fantasy draft?
(Other top-30 all-time seasons: 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1996)

2. Shawn Marion
Position: SF
Year: 2006
Player Rater: 15.15
You're shocked by this, right? I know I was. But this was no great fluke -- Marion was only a little better by the fantasy formula than the season before.
Here's what was going on: First, Marion was at his best, playing off MVP Steve Nash. He averaged a career-best 21.8 points and played more than 40 MPG. He shot a career-best 52.5 percent from the floor and hit a decent percentage from deep. He averaged a career-high 11.8 boards and finished fifth in the league in SPG. He reached another career-best average with 1.7 blocks. It was simply a rare combination of across-the-board numbers.
(Other top-30 all-time season: 2005)

3. Larry Bird
Position: SF
Year: 1988
Player Rater: 15.09
Bird did everything well. A lot of people forget that he was a double-digit rebounder for his career. His steal totals reflected a preternatural ability to read the passing lanes, and he even had a knack for timely blocks in help situations. And of course he was the best passing forward of all-time up to, and maybe including, LeBron James. (That's a heck of an argument for a rainy night.)
In 1987-88, Bird hit a career-high 98 3-pointers in a season in which only five players averaged even one trey per game.
(Other top-30 all-time seasons: 1983, 1985, 1986, 1987)

4. Dirk Nowitzki
Position: PF
Year: 2005
Player Rater: 14.96
Nowitzki enjoyed a number of similar seasons during his prime. The 2004-05 season wasn't his MVP run, but it was his best fantasy campaign.
He averaged career-highs in rebounds (9.7), assists (3.1), steals (1.2) and blocks (1.5) while putting up 26.1 points, all with his trademark efficiency.
(Other top-30 all-time season: 2003)

5. Kevin Garnett
Position: PF
Year: 2005
Player Rater: 14.68
Like Nowitzki, Garnett's top fantasy season does not coincide with his real-life MVP award. That's despite the fact that his numbers in 2003-04 were at career-best levels pretty much across the board. But the way the Player Rater works, it's not just a matter of your categorical totals. It's a matter of those totals as compared to everyone else in the league, with a premium on the scarcity of those contributions.
I haven't been able to put my finger on what it was, but there was something about the 2004-05 season that resulted in a few of the best individual seasons from that season ranking high on the all-time leaderboard. Anyway, KG was really good that season.
(Other top-30 all-time season: 2004)

6. Stephen Curry
Position: PG
Year: 2016
Player Rater: 13.24
If you haven't noticed how otherworldly Curry's game has become, you're almost certainly not reading this story. With Draymond Green taking on the role as primary playmaker for the Warriors, the fantasy value of Curry's assists has actually declined.
Safe to say he's made up for it in other ways.
(Other top-30 all-time seasons: 2015)

7. Peja Stojakovic
Position: SF
Year: 2004
Player Rater: 12.85
Stojakovic had a fine career, but he was out of his mind in the 2003-04 season. He put up a career-best 24.2 points while hitting 43.3 percent from deep and leading the NBA in total 3s. He shot 92.7 percent from the line on 5.2 trips per game. He also chipped in with career bests in most of the floor-game categories while playing more than 40 MPG.
It was noticed at the time: Stojakovic finished fourth in MVP voting that season.

8. Kevin Durant
Position: SF
Year: 2013
Player Rater: 12.78
This was the season before Durant's MVP trophy.
In 2012-13, Durant reached peak efficiency. He put up a ridiculous 64.7 true-shooting percentage, while joining the coveted .500/.400/.900 club with his shooting stats.
(Other top-30 all-time season: 2014)

9. LeBron James
Position: SF
Year: 2005
Player Rater: 11.95
My version of the Player Rater formula is a little hard on LeBron. That's because of the inclusion of turnovers. James has ranked in the top 10 league-wide in turnovers in 12 of the past 13 seasons. Since it's a fairly small subset of players who rack up big turnover totals, they carry a disproportionately large negative marginal value. That's OK -- we know how great LeBron is.
James has been incredibly consistent throughout his career. What makes this season stand out is his steal total: James had 39 more steals than he has had in any other season.

10. Hakeem Olajuwon
Position: C
Year: 1993
Player Rater: 11.52
Hakeem was always a fantasy dream, but it was in the 1992-93 season when he focused more on finding teammates off double teams. He was at his peak, putting up huge rebound, assist and block numbers to go with his scoring and passing, and he shot 52.9 percent from the floor.
Other players with top-30 all-time seasons: Magic Johnson (1990), Reggie Miller (1991), Ray Allen (2001) and Chris Paul (2015).