Brandon is known to be a very efficient player who doesn't make mistakes. His 2nd team all-NBA recognizes his status as among the leagues best four active guards. But Brandon's last season was really remarkable among NBA guards throughout history.
I used the "full court" part of basketball-reference.com. I arbitrarily looked just at the last 25 years, from 83/84 to 08/09. I looked for guards that played 2650 minutes or more, which is 36 minutes times 82 games less 10% for injuries.
His PER was 24.0, which is really good but not what makes his season unique. What makes his season unique is the low rate of mistakes while being a key part of his teams offense and delivering the ball to his teammates for assists. This season, his turnover percentage (TOV%) was 9.0%, his usage percentage (USG%) was 27.5%, and his assist percentage (AST%) was 25.4%.
I looked in history for guards with seasons that have equaled or bettered each of these numbers. Only two seasons showed up: Jordan 91/92 and Carter 04/05. Both players were 28. Brandon was 24.
I then looked for seasons that were within 10% of Brandon's numbers: TOV% <= 9.9, USG% >= 24.8, and AST% >= 22.9. These allow for 10% more turnovers, 10% less usage, and 10% less assists. This allows for players that were a bit more careless with the ball (but still quite good), a bit less of the focus of their team's offense, and handed out a bit less assists.
Seasons from only four players showed up: Jordan five times (87/88, 89/90, 90/91, 91/92, 92/93), Brandon twice (07/08, 08/09), Carter twice (04/05, 08/09), and Kobe twice (05/06, 08/09).
To be in this company at so early in his career and at such a young age is remarkable. Brandon has done it twice, in his 2nd and 3rd years. Jordan did it 4, 6, 7, 8, and 9 years into his career. Carter did it in years 7 and 11. Kobe did it in years 10 and 13.
So Brandon, early in his career, is playing like the best years of these clear Hall of Famers and all time greats, in terms of high efficiency, low mistake basketball.