Madden - 34 years old
Pokemon - 26 years old
FIFA - 29 years old
Mario Kart - 30 years old
Call of Duty 20 years old this year! (23 if you count back to Medal of Honor)
God of War - 17 years old
Gran Turismo - 26 years old
https://www.statista.com/statistics/1285658/top-ranked-video...
Elden Ring may not be a narrative sequel, but it is definitely a mechanical sequel in the line of From Software games stretching back to Demon Souls in 2009, which makes the series 14 years old. It's innovative in its series, but I wouldn't praise it for a wealth of conceptual originality.
There's also an inherent bias with looking at the Top Sellers - for a game to be bought by lots of people, it has to be known about by lots of people. Brand recognition makes that easier, so even if studios are innovating all the time, you would still expect existing series to show up much more than new IPs. It would take an exceptionally strong game, with good marketing, to break into that list.