Peterson wasn't perfect, I'd probably have him outside the top-10 of all-time, but that is some pretty huge nitpicking. I can really only think of 2 major fumbles in Peterson's career, and neither of those swung the the game. they still beat Seattle in 2016(in the coldest game in NFL history) if Walsh makes a gimme FG, and they still beat NO in 2010(a game Peterson had 120 yards and 3 TD's in), if Favre doesn't throw that horrible across the field INT. So really, I'm not sure any of Peterson's fumbles were that huge of a deal.I'll give you that Adrian was a better athlete. But his key fumbles in big games are a huge weakness.
Walter Payton was annually among the fumble leaders, and he's universally considered a top-3 RB of all time. Much rather have guys who took over games and occasionally made mistakes, than good players who didn't make mistakes.