Truth is, even during the regular season Bart Starr was better than "above average" and was statistically one of the best QBs in football year after year. He was the highest rated passer 3 times and finished with a career rating of 80.5 at a time when the league rating was usually in the mid 60s. He's another guy who threw more TDs than picks for his career when the league as a whole threw far more interceptions than TDs. His career totals in yards and TDs just aren't eye-popping because Vince Lombardi was his coach. Let's not pretend he was just some OK guy who suddenly turned into a beast during the post-season. He was great all the time. I'd argue that without the titles, he's still a HoF worthy player. Only a handfull Of players of his era or earlier have the raw stats to compare to his, without the adjustments of advanced passing: Otto Graham (criminally overlooked in this thread), Sonny Jurgensen, and Len Dawson. And this is regular season ONLY. However, we can't separate the man from the titles. The fact he was so great in winning 5 of them is what gets him into the conversation for being called the GOAT. He won them because he was great, not the other way around.
The opposite is true of Eli. Eli is not a great QB, he has just made a couple of great runs. To make the HoF, I think you should be truly great. Like Warner (I think), I put more emphasis on the regular season because that's the overwhelming majority of any player's career. What he does during the playoffs I do weigh more than the average game, because the situation is the most pressure-cooked atmosphere they'll ever be in. It's all on the line. That said, I can't say let's put an average guy into the Hall because he was great twice in the playoffs.
As all of this relates to Peyton and who is the GOAT. I'll definitely listen to the argument that Starr is that guy. I'd do the same for Montana, Graham, Unitas, Brady, Tarkenton and Peyton. For me, there is a clear line of demarcation between this group and whoever is in the next tier. Playoff performance does figure into this. Having no titles is a knock on a guy (as a QB, I don't do this for any other position in football). Hence, I would put Tarkenton at the bottom of that list and I don't include Marino at all, another regular season king. I've seen Montana, Brady, and Peyton with my own eyes and I'd take Manning over the three of them (and I grew up a Montana guy). Manning truly changed the position. Not many players in the history of any sport can say that. Still, I probably lean toward Graham and Unitas. They also changed the sport and were both just playing a different game than their contemporaries.
