For at least half of his reign, the featherweight division virtually existed only within pro Shooto, meaning that he [Alexandre Nogueira] was the best fighter of about two dozen total in his weight class, beating the likes of Tetsuo Katsuta and Stephen Palling. From about 2004 onward -- when opportunities began to crop up for featherweights globally and the division began to broaden -- he fought sparsely, and against none of the top emergent talents, until his smashing last year at the hands of supernova Jose Aldo.
Beating your best contemporaries is always the measuring stick for prizefighting, but there does need to be some sort of baseline of quality established. It's the same reason it's asinine to compare the accomplishments of Royce Gracie and Fedor Emelianenko. As soon as featherweight became a legitimate, serious division, "Pequeno" was done. Though I'm sure his knee troubles didn't help, his losses to Hideo Tokoro and Jose Aldo affirmed that he was no world-beater. It's little wonder he so cravenly ducked Gilbert Melendez three years ago.
The featherweight division is now a full-fledged galaxy, with global giants rather than regionalized dwarves, replete with luminosity and magnitude (how much longer can I milk the astronomy angle?). In this modern division, Brown is the first fighter to truly reign over other great fighters to any extent.