The Case For: Unitas was a three-time NFL Champion, including in 1958, when the Baltimore Colts won the Greatest Game Ever Played in overtime. He was a 10-time Pro Bowler and three-time Pro Bowl MVP (back when that meant something), four-time NFL MVP, five-time first team All-Pro, two-time second team All-Pro. He made 1960's NFL All-Decade Team, NFL 50th and 75th Anniversary All-Time Team. His No. 19 Colts jersey is retired, and the Baltimore Ravens have not issued that number since Scott Mitchell wore it in 1999. 1979 Hall of Fame inductee. His records for Pro Bowl appearances stood until Brett Favre broke it in 2009. His record for most consecutive games with a touchdown pass (47) lasted until 2012 when Drew Brees broke it. His record of four consecutive games with a passer rating of 120 still hasn't been broken. Unitas was a passer who was ahead of his time.
The Case Against: Nothing against him specifically, but Unitas and the Baltimore Colts only came away with one Super Bowl during the rest of his career, and Earl Morrall replaced him after he suffered a concussion in the first quarter.
The Case For: Four-time Super Bowl winner, three-time Super Bowl MVP, eight-time Pro Bowler, three-time first team All-Pro, two-time NFL MVP, two-time second team All-Pro, NFL 1980's All-Decade Team, NFL 75th Anniversary Team, Hall of Fame Inductee in 2000. Statistically, he's the second best postseason QB ever, and his record of 12 playoff games with a passer rating over 100 still stands. His San Francisco 49ers No. 16 jersey is retired.
The Case Against: Tom Brady has surpassed most of his postseason records. and has as many Super Bowl rings and MVPs as Montana now.
The Case For: Two-time Super Bowl winner, one-time Super Bowl MVP, nine-time Pro Bowler, two-time second team All-Pro, 1987 NFL MVP, 1990's All-Decade Team. His Denver Broncos No. 7 jersey retired. Hall of Fame inductee in 2004. Fourth-winningest QB ever, sixth best rushing QB ever and fifth most prolific QB ever.
The Case Against: Elway lost three Super Bowls in horrific fashion, and fared poorly in all of them.
The Case For: Nine-time Pro Bowler, three-time first team All-Pro, three-time second team All-Pro, 1984 NFL MVP, first QB to throw for 5,000 yards in a single season (1984). He was the first QB to throw for 40 touchdowns (48 in 1984) of his records still stand, including most games with 400 yards passing. He also has the most seasons leading the league in completions, most seasons leading the league in the lowest sack percentage, 100 touchdown passes in fewest games, and 200 touchdown passes in fewest games.
The Case Against: Many of his records have been surpassed and he made it to only one Super Bowl and lost it.
The Case For: He's the only quarterback to throw for 70,000 yards, 6,000 completions, and over 10,000 attempts. An 11-time Pro Bowler, three-time first team All-Pro, three-time second team All-Pro. Only QB to win MVP three straight years (1995-1997). One-time Super Bowl champion. NFL 1990's All-Decade Team. Most regular season wins by a starting QB with 186. Most consecutive regular and postseason games played with 321. And many,many other records and firsts that still stand. 4 time NFL Passing TDs leader (1995-1997, 2003)
The Case Against: Favre also has the NFL interceptions record with 336, a record that nobody can touch. Many of Favre's records have been overtaken, including his touchdown record that Peyton overtook. Favre had a tendency to throw horrific interceptions at inconvenient times, and he has the second highest amount of postseason losses in NFL history. His frequent flirtation with retirement. The Jenn Sterger incident. The fact that he only won one Super Bowl despite playing for 20 seasons and being a starter for 19 of them.
The Case For: Manning is a 14-time Pro Bowler, seven-time first team All-Pro, three-time second team All-Pro, five-time NFL MVP (2003,2004,2008,2009,2013) and four-time NFL passing touchdown leader (2000, 2004, 2006, 2013)/ NFL All-Time Leader in touchdown passes with 530, on-time Super Bowl Champion, one-time Super Bowl MVP, most Pro Bowl Appearances by any NFL player. NFL 2000s All-Decade Team, Has set the NFL record for most TD passes in a single season twice with 49 in 2004 and 55 in 2013. He also has a fair chance to attack Brett Favre's record for passing yards. He also holds many other passing records.
The Case Against: His game has a noticeable decline in the postseason. He has the NFL record for most losses in the playoffs (13) and most one-and-dones (9). He won one Super Bowl, against Rex Grossman and the Bears, and didn't do too well in that postseason, throwing two touchdowns vs. seven interceptions. He's lost two Super Bowls, throwing the game sealing pick-six to Tracy Porter in Super Bowl XLIV, and he had a dreadful performance against the Seahawks in Super Bowl XLVIII. The notion that his statistical excellence was a result of playing with the following stars: Marvin Harrison, Dallas Clark, Reggie Wayne, Edgerrin James, Joseph Addai, Demaryius Thomas, Eric Decker, Wes Welker, Brandon Stokley, Julius Thomas, as well as many other talented receivers.
The Case For: Brady is the winningest playoff QB ever, with a 21-8 record. Longest consecutive winning streak in NFL history with 21. Four-time Super Bowl Champion and three-time Super Bowl MVP. Two-time NFL MVP (2007, 2010). Two-time first team All-Pro, one-time second-team All-Pro, 10-time Pro Bowler, three-time NFL passing touchdowns leader (2002, 2007, 2010). Two-time NFL passing yards leader (2002, 2010). NFL 2000s All-Decade Team. Most division titles for a QB with 12, Most career Super Bowl touchdown passes, Most pass completions in a Super Bowl and most pass completions in the playoffs. First QB to throw 50 touchdown passes in a season. Only QB to play in six Super Bowls. Often got the job done with mediocre skill players, with the exception of Randy Moss, Rob Gronkowski, Wes Welker, and Corey Dillon.
The Case Against: Joe Montana never lost a Super Bowl.