The series depicts a gladiator as an individual without rights, but not without reward for his wins. In both Scott's Gladiator and Kubrick's Spartacus, the galdiators are slaves - and are treated as such - whereas the series shows how being a lanista was a profitable business and how keeping your men alive, indeed, cultivating a Champion, would have been desireable. The gladiator's costumes are not representitive of the actual things and the gladiators' personal lives are not really explored. The film, Gladiator, is about revenge set in ancient Rome. But, it did not give a good depiction of a galdiator's life, and THAT'S where the STARZ show is best. It also captured a very gritty, authentic feel similar to Braveheart (which the modern show lacks because it was filmed in a green-screen studio, for example). It's story was closer to an actual historical narrative than say, Fall of the Roman Empire, Quo Vadis or Ben Hur. Its props and costumes were ahead of the rest of the sword/sandals epics.
Kubrick's Spartacus was the best of the three.