Ortho Stice wrote:A statistic like that may tell us that someone else is more clutch than Kobe, despite his ridiculous amount of game-winners.
Actually Bryant has that many game-winners, because he takes so many shots which can result into a game-winner. His scoring efficiency on game-winners is rather bad, in fact worse than his average scoring efficiency. I don't think that the amount of game-winners is a good indicator for being "clutch".
The graphic in the op doesn't show it, but from those players Bryant has the lowest fg% on those shots, LeBron James the highest; slightly ahead of Nowitzki. Carter is closer to Bryant, but still better in terms of fg%.
Ortho Stice wrote:I think a statistic on clutchness should look at the very end of games, when the shot directly involves his team tying the game, or taking the lead, with the opposing team only having one possession afterward; this will account for clutch shots made with time left on the clock. And I think the amount of clutch shots hit needs to be leavened with the % of clutch FGs to clutch FGAs.
Sorry, but that isn't a good measurement. The dagger with a minute left isn't less valuable than the game-winning buzzer beater.
I take Bryant's game-winners in this season so far as an example. Against the Heat Bryant was the player who missed a shot with 25 seconds left, he missed the layup with 14 seconds left and Fisher made the 3 with 4 seconds left to give the Lakers at least a chance. Bryant's game-winning three was a lucky off-balance shot. Was that really a great clutch performance? 
Against the Bucks Bryant missed a shot with 1:50 left in regulation, he missed the shot with 2 seconds left, Fisher made the basket with 31 seconds left in regulation to give the Lakers the lead. In the last 1,5 minutes Bryant took over, a great clutch performance, but the win was also a result of the inability of Ilyasova to make his free throws. Would Bryant's effort being less clutch in OT, if the Lakers had lost, because Ilyasova would have made his free throws?
With 2,5 minutes left in the game against the Kings Bryant missed both of his free throws and a possible game-leading 3pt shot. After that Lamar Odom, Pau Gasol and Shannon Brown brought the Lakers back into the game. Bryant got away with a potential offensive foul as he set the screen to get open for the game-winning 3. And again, without Udoka missing both free throws with 4 seconds left a 3pt wouldn't be enough to win that game. Besides the last second shot it wasn't really that great of a clutch performance by Bryant.
In the game against the Celtics Bryant was 2 of 7 from the field in the 4th quarter, made 6 of the 24 points for the Lakers. Not even one of the other baskets was assisted by Bryant in the 4th quarter. Artest made the basket to bring the game within 1 point, after that he took the charge against Paul Pierce to give the Lakers the possession. Bryant took a really tough shot against Allen. It was a great fadeway shot, no question, but was Artest less clutch than Bryant in that game? Would Bryant be less clutch, if Allen would have made the buzzer-beating 3 to give the Celtics the win?
Bryant scored 9 points in the last 2 minutes against the Grizzlies. Incredible clutch performance to erase a 5 point deficite. Would that be less impressive, if Mayo would have made the buzzer-beating 2 pointer to win that game for Memphis?
As you see your definition depends a lot on the situation while just using a bigger time span gives you an overall better picture. Bryant isn't as a clutch as James or Nowitzki in this season. Just look at their impressive Net48 numbers. The Mavericks are +29.4 per 48 minutes in clutch situations (according to 82games.com) while Nowitzki is on the court, the Cavs are +30.1 with James. Compare that to the Lakers and Bryant with +11.7.
Nowitzki and Bryant are scoring around the same amount of points with the same scoring efficiency, but Nowitzki is the better rebounder and has already 7 blocked shots during clutch time. Nowitzki is even the better passer with 15 assists and 0 passing turnovers compared to Bryant's 10 assists and 2 passing turnovers. James scores nearly 20 points per 48 minutes more on a higher scoring efficiency, has more assists, more rebounds, more blocked shots than Bryant.
Overall if there is a close game (using the definition by 82games.com) it is more likely in this season to win with James or Nowitzki on the court as with Bryant on the court.
So, a clutch shot for me is a shot in a critical possession for the team. Maybe stopping a run in the 4th quarter with that or providing the dagger to give the team a significant lead. A game-winner is a game-winner, quasi a special clutch shot defined by the situation.