Out of all the players in this slideshow, not a single player was better once they left the Lakers or before they joined the Lakers, and, as an extension, Kobe Bryant.
From role players to starters, Sixth Man of the Year winners and second option on offense, there is literally no one who left Lakers a better player, and in the same vein, there is no one who joined the Lakers and became a worse player. (Well, except Ron Artest, but he has been consistently declining at any rate—same with Fisher and Steve Blake.)
Among all of Kobe's teammates in his post-Shaq career, only Caron Butler managed to improve compared to his time with the Lakers. Even then, it's probably more due to his maturation (he was a third-year player during his time with the Lakers) compared to Kobe actually stifling his talent.
If anything, Kobe somehow miraculously makes terrible players look average, good players look great and D-Leaguers Sixth Man of the Year winners. Assist averages does not necessarily determine one's ability to make others better, nor even the ability to share the rock, otherwise Stephon Marbury is a generous point guard (he's not) and Derrick Rose is a shooting guard in a point guard's body (he's not).
Kobe makes his teammates better by doing one thing and one thing only: scoring. By drawing defensive attention away from his teammates, they all have the opportunity to take a much higher-percentage shot with less defensive coverage. Or they can grab a rebound uncontested or even make an additional pass from Kobe's lead pass, which leads to an assist.
Unless, of course, you're Steve Blake, who repeatedly receives wide-open threes and bricks it more often than not.
Coincidentally, LeBron James—the King, the Chosen One, the Oscar Robertson of our era, the pass-first hybrid scoring machine and triple-double god—has a much less stellar record of so-called "making his teammates better," with Wade, Bosh, and even Antawn Jamison playing better in his absence.
Even now, Anderson Varejao is having the best season of his career without LeBron, and despite Mo Williams obtaining his sole All-Star status during his time with the Cavs, he has been much more productive during his time with the Clippers.
Chris Paul is making him better, perhaps?
Before he started winning championships, Jordan was also considered unable to make his teammates better, and he angrily dismissed those reports by reportedly saying "You can't make chicken salad out of chicken (bleep)."
I guess in the case of Kobe Bryant, he not only makes chicken salad out of chicken (bleep*), but adds in some salad dressing and high quality Kobe-grade beef as well.