James is a great player. He was blessed with some of the best physical attributes you could ask for in a basketball player. He's like a create-a-player from some of those video games. However he will never be considered the best for various reasons- which right now is him losing so many Finals.
James definitely has never had the great coaching of someone like Phil Jackson or Popovich, and lacked the great supporting casts of some of the past NBA legends. However where James seems to lack the most consistently, to me, is mentally. He just doesn't seem to possess that killer instinct that say Jordan had. Nor does he seem to have the same will to win either.
He'll never be considered the GOAT but when all is said and done he'll still be up there with most of the NBA greats of the past.