And there's a differentiation to be made there.
People have contended that Rousey is the best fighter on Earth. She isn't. She's a hyper-competitive, super-elite athlete who is fighting neophytes in a sport that is, itself, barely fumbling out of adolescence.
She is, however, one of the greatest show-persons in the sport, a star who transcends mixed martial arts and routinely finds herself starring in films, bulldogging her way into headlines at the expense of others and charming late-night talk show hosts and the crowds that follow them.
This penchant for showmanship extends to the cage as well. People are interested in watching Rousey fight because she's capable of unleashing ferocity the likes of which isn't often seen in MMA, much less in the real world.
As she heads into another title defense at UFC 190, against Bethe Correia, a challenger who hadn't thrown a punch in her life until well after Rousey was among the most decorated American judokas in history, most believe she'll add another scalp to her collection—and do so easily. Talk has shifted, even from Rousey herself, to her legacy—what it is now and will be when people examine things down the line.
That legacy should be one founded on showmanship more than competitive greatness.
Rousey is an undeniable trailblazer, the woman who turned Dana White from a man who believed hell would freeze over before ladies entered his world to a man who routinely celebrates both her and the division she created as the best things he ever did for the UFC.
She is a wonderful martial artist, the type who devotes herself to her craft and being the best version of herself she can possibly be. That drive helps as much in making her dominant as the fact that her challengers are light-years behind her.
But what people should recall when Rousey is long gone, making movies, having children or moderating a Pokemon forum, is the fact that she was among the best shows MMA had when she did compete. From her entrance music and her game face to the inevitable slaughter that follows, few things compare to what she brings to the sport.
That isn't, however, to mistake her for being the best fighter the sport has ever seen. It shouldn't indicate that she's even the best fighter presently fighting. Greatness is relative to the competition one faces, and simply being way, way better than the opposition—which is between weak and middling—is not enough to make one the best.
There's nothing wrong with that. The danger is conflating putting on a show and providing intrigue and entertainment for fans with a legacy of greatness. Without a fight against Cris Cyborg the only proper competitive challenge out there (though if she were 135 pounds, Joanna Jedrzejczyk would warrant some attention), there'll never be any way to know if Rousey is the best talent of her generation.
So when she says she's fighting for legacy instead of money or fame at this point, that's fine. Everyone interested should be fully aware of what that legacy is, though: Rousey is the greatest show(wo)man in the sport. Everything else is just window dressing.