I definitely think as time passes, people forget just how great Payton was. He is my favorite player of all time.
He WAS the offense.
QBs he played with: Bob Avellini, Bobby Douglass, Gary Huff, Virgil Carter, Vince Evans, Mike Phipps, Jim McMahon, Steve Fuller, Greg Landry, Rusty Lisch, Mike Tomczak, Doug Flutie, Jim Harbaugh. Heck, Payton himself lined up at QB a few times. Basically, Jim McMahon was the best he played with. That's not saying much.
Payton played with 1 Pro Bowl QB in 13 seasons: McMahon in 1985. (And why exactly did McMahon make the Pro Bowl? The Bears passing offense was 22nd in yards and 23rd in TDs... McMahon threw for 2392 yards and 15 TDs.)
Not only did he never play with a 1000 yard receiver, he never even played with a 900 yard receiver. In fact, only 3 times in his 13 year career did any Bears receiver top 800 yards, and only 3 other times did any Bears receiver top 700 yards. And there were no good receiving TEs, either. It should come as no surprise that no Bears WR (or TE) made the Pro Bowl during Payton's career.
To reinforce this, consider Chicago's pass yardage ranks during Payton's career: 23 (of 26), 28 (of 28), 21, 26, 26, 28, 28, 22, 17, 26, 22, 24, 14. They finished in the bottom quarter of the league 10 times in Payton's career.
Payton himself led the Bears in receptions 6 times, and had the second highest total 5 other times.
In his last few years, his offensive lines were pretty good, but for most of his career it wasn't. Two of Payton's linemen made the Pro Bowl a total of 5 times in his 13 seasons, all in his final 3 seasons: Jim Covert (1985, 1986), and Jay Hilgenberg (1985, 1986, 1987).
Despite the lack of support, he retired as the all time NFL leader in rushing yards, yards from scrimmage, all purpose yards, and rushing TDs. He retired #1 in receptions and #2 in receiving yards for a RB in NFL history. He retired with the most 100+ yard rushing games and 1000+ yard rushing seasons in NFL history. And after missing a game in his rookie season, he didn't miss another game in the rest of his career, playing 186 straight games.
Aside from all that, Payton was arguably the most well rounded RB in history. He was a great runner, receiver, and blocker. He ran equally well to the outside and up the middle (or over the middle). He was great in short yardage and goalline situations as well as other running situations. He was the Bears' emergency QB, and he passed for 8 TDs in his career. He was the Bears' emergency kicker and punter for part of his career. He didn't return many kickoffs (17), but he averaged 31.7 yards per return, and led the NFL in kickoff return average the one season that he returned more than 2 kickoffs (1975). He was also known as a great leader, and he was such a great person and class act off the field, the NFL's man of the year award is named after him.
I think for all these reasons, he is the best RB, and possibly the best football player, in NFL history.