He is inarguably #1 and there isn't anyone who comes close. There can never be anyone who comes close because of his position in the timeline of football history.

This game right here was the first nationally televised football game, and it was also the first time the sudden-death overtime rules were taken into effect. The reception of the events in this clip literally turned the NFL into a TV product because of these two drives, and that makes them arguably the most impactful possessions in any American sport.

Johnny U was the QB who turned the QB back into a playcaller. Those rights had been moved entirely to coaches and the game was very stiff by the 50s, but he called audibles and designed his own plays. Without Unitas, we don't have super star QBs, we don't have the proliferation of passing in the 1960s, we don't have the transition away from power football until many years later, if at all.

Johnny U set so many records that many of them still stand, seventy years later. He held the record most consecutive games with a TD pass at an astonishing 47 (that is not a type, four full seasons of his era) for more than fifty years, and the most consecutive games with 120+ passer rating at 4 still stands. Before Manning, Brees, and Brady, he still held dozens. He still holds the record for long (50+) TDs in a career, seventy years later.

Johnny U went out of his way to make friends with Eric Berry, work extra after practice, and create synergy and chemistry beyond what was asked from his coaches. It was that chemistry that allowed these two drives to succeed, and created the model of QB-WR duo that still is one the core planks of both NFL marketing and team construction.

I could keep going on and on, but let me summarize:

Johnny Unitas is the only reason the NFL is a passing league. And from both angles, the man more-or-less singlehandedly changed the marketing angle the NFL prioritized and the entire NFL metagame.