1. Matt Ryan
Looking at franchise history it doesn't matter how far you turn the clock back Matt Ryan will always be at the top of any honest list. This isn't to discredit Chris Chandler or Michael Vick, but rather an objective answer of who had the most impact on the franchise. Ryan's legacy is going to be a difficult one to untangle due to the infamous Super Bowl and the franchise consistently failing the veteran quarterback.
While many pundits are quick to point out Ryan's great targets throughout his tenure they won't tell the full story. How many times did Ryan have a capable offensive line, defense, and a running game? If all three were anything close to capable the quarterback had the Falcons in the playoffs. This is despite never having the benefit of being coached by a great leader.
Mike Smith was arguably the best fit Ryan ever was given with Dan Quinn the only other possible answer. Ryan never made excuses or threw his front office or team under the bus. He showed up clocked in and gave the franchise everything he had in the tank. All you can ask of a franchise quarterback is what Ryan gave leaving his legacy cemented in franchise history.