With all the chatter lately about the necessity of having an 'elite' quarterback I wanted to explore what exactly makes one elite, who the current elites are and who will be elites of future. 
My personal definition of an elite quarterback encompasses four main ingredients:
1) Leadership
2) Rising to the occasion
3) Longevity
4) Winning
You may have noticed I made no specific mention of personal statistics. For me, stats are overrated. If a guy has great stats with a strong supporting cast but doesn't lead his team to victory what does it matter? 

If he doesn't have great stats or a particularly good supporting cast but does lead his team to wins, well - I think you get my point. 
An elite quarterback must lead his team. He doesn't have to be a vocal leader. Eli Manning is a shining example of that truth. Whether by word or deed, leadership is a prerequisite to winning a championship in today's NFL. 
Rising to the occasion is obvious. Under extreme pressure and/or adverse circumstances, can the quarterback will his team to victory? All the elites do. 
Can a guy be considered an elite quarterback if he is inconsistent from year to year, only occasionally performing at optimum efficiency? I would argue not. All of the game's currently acknowledged elites have been performing at a high level for several years or longer. 
Winning. Although it sounds obvious, winning could be the least of the considerations given a particular circumstance. That circumstance being a truly great quarterback on a really bad team.

But even then his greatness will shine through often enough to win games, or put his team in a position to win,  in spite of the obvious handicap.  
The general consensus is that there are currently six elite NFL quarterbacks. They all share the aforementioned qualities. In no particular order they include Brady, Brees, Rodgers, Roethlisberger and the Manning brothers. 
If and when Phillip Rivers at least takes his San Diego Chargers to the Super Bowl, he will probably join the list. For any of the league's other more tenured quarterbacks (five or more years), it would probably take a couple of Super Bowls at the least to make the jump. 
In regards to the up-and-coming elite quarterbacks of the future, the best criteria we have at the moment is the eyeball test. Who looks like they have the potential to become elite? Who seemingly embodies the qualities necessary to join this ranking?
My list is headed up by two young quarterbacks. They are Matthew Stafford of the Detroit Lions and Cam Newton of the Carolina Panthers. 
Stafford is coming off a phenomenal year in his 3rd NFL campaign, after suffering through an injury-riddled first two seasons. He threw for almost 5,000 yards in leading Detroit to the playoffs for the first time in 12 years.

He played with heart and guts, was clearly the leader of the offense and engineered impressive late-game comebacks. Now all he's got to do is steady his game, continue growing, and show he can perform at his current level in the playoffs. 
Cam Newton looked in his rookie season as though he has the potential to be the elite of the elites. He appears to have it all. A sensational athlete with a great - and more importantly - accurate arm. It does remain to be seen how he performs in his sophomore season before anointing him just yet. 
Which is my segue to the next cluster of possible future elites, headed by Sam Bradford.  
Bradford, like Newton, had a great rookie campaign. But he fought his way through an injury-plagued sophomore season on a team decimated by injury. Had that been his rookie season, there would be talk of him being a bust. I think Bradford will develop into an elite quarterback. 
Another possibility is Matt Ryan. Ryan went from being a possible 'great one' to 'he can't win the big one' after bowing out of the first round of the playoffs for the third time in three tries.

Of course, Ryan was selected 3rd overall in the 2008 Draft because Atlanta was a bad team in total disarray. Adding Ryan was enough to propel them into the playoffs his rookie season, and twice again after missing the playoffs in 2009.

In 2009 the eventual world champion Saints beat the Falcons out for the division title. Ryan just needs to turn around his playoff fortunes and he will likely join the elites. 
Other possible candidates are Joe Flacco, Mark Sanchez (hey - he led his team to two AFC championship games his first two seasons), Andrew Luck and Robert Griffin III.
It's clear what Flacco and Sanchez need to accomplish. Take the next step and win a Super Bowl. 
Luck and Griffin are purely speculative at this point. But seeing as they are almost unanimously considered as being two of the best college quarterback prospects to come out of the Draft in years, it appears to be a good bet. 
Did I miss anybody?