In the modern recently era, I think CCC was earlier than Khabib. It was sad khabib retired when he did, but we gotta remember Khabib had been a pro MMA fighter since 2008 (13 years) and in the UFC since Jan 2012. So 9 full years in the UFC. He was just marred with some inactivity and missed fights. That's a pretty good run.
CCC on the other hand was only doing MMA for like 8 years and had really only hit his stride the few years of this imo. He had more to give and show imo. Would've liked to see him get a few more bantamweight defences.