Seeing as this pops up ever so often (and a lot this season), let's do a true, contextual Manning and Favre comparison for Winston to end the discussion.
What I did was pulled the rankings in various statistical categories for the 3 QBs. So where that season did the QB rank in INTs, TDs, etc. Low numbers are always good.
*For injury or suspension shortened season, I extrapolated the relevant statistics and denoted those seasons with an asterisk. So if Winston threw 10 TDs in 10 games, I extrapolated that season to 16 TDs and put in that ranking.
*DYAR is Football Outsiders' DVOA but on a per play basis.
*I also included Cutler because... well you can see why.
*Winston's numbers are completely incomparable to Favre and Mannings. The only other argument is that somehow the team influenced these statistics. Those arguments have been refuted numerous times (for example, a bad defense often inflates QB stats). But even then, Manning over these 5 years probably had a worse defense and run game than the Bucs.
If its not readable, let me know.