When the Infinity Gauntlet storyline initially started up in the comics, Thanos notes that to wield the gems takes an extraordinary amount of not only physical strength, but strength of will and mental resilience.
As others have noted, the Kree are an exceptionally strong race (on par with Asgardians), and Ronan was certainly strong-willed. Being such a petulant, ego-maniacal fanatic, one can't be sure he'd have withstood the mental stress of the gem had he held it any longer than he did.
Even wielding it through some kind of conduit (scepter, hammer, gauntlet) leads to gradual degradation of sanity in the comics. This has yet to be established in the MCU, but it would certainly be in keeping with the behavior of wielders we've seen so far, so it's a point to consider.
Another important note: Nova Prime mentions at the ends of GOTG that Star-Lord's genetic makeup included DNA from an alien species with no known record. Quill is only HALF-human, which most likely helped him withstand the stress of the gem.