Curtis Martin is one of the most overrated RBs in history. He was a very good RB for a decade, he was never elite, not sure he was ever one of the 3 best RBs in the NFL at any point of his career, and he was absolutely a statistical compiler. I can't even understand an argument that Martin was better than Peterson. Peterson had more power, burst, more ability to just take over a game. Martin was better in the passing game, and more durable and that's it.
Tomlinson obviously had more versatility, but never had Peterson's power, and he showed signs of decline a lot sooner. There is an argument that they were equals, depending on what type of offense you like to run, and what you are asking a RB to do, but purely as a runner, Peterson was simply better.
I'm starting to think Adrian Peterson is one of the most underrated players in recent history. Without him, the Vikings are probably picking in the top-10 for almost the entire last decade.