Vick's a poor example. At least, I don't think it's the same "mental fortitude" issue that we're talking about here. Vick was just never that good of a quarterback. Ever. Some of could be described as "mental" - in that he was a poor reader of defenses - but it wasn't like he was world-class in every way except for the fact that he didn't come through in the clutch, or wasn't a champion, or didn't have a killer instinct, or couldn't handle expectations. He had severe flaws as a player that prevented him from even being in this discussion. We're talking about true greats who, for one reason or another, didn't have that one mental ingredient to put them over the top. Like LeBron eschewing any chance of being in Jordan's class, opting instead to be Magic/Pippen. (Still a pretty great thing, but no Jordan.)
At least that's how I interpreted the question.
