The old-timers, products of a long gone era, might be more racist, more homophobic, or have insane religious beliefs that would dismay modern sensibilities, or -- even more interestingly -- they might be surprisingly progressive. Their stories could be told Ken Burn's style, or Real Housewives style (they probably have some nutty progeny, the odds favor it), but no matter what style of documenting them was used, there must be a wealth of a stories in each of their lives. Some will probably be in hospital beds hooked up to machines: opportunity to examine end of life care. Some will probably be spry old Okinawan fish-mongers or something, working 'til the last day of their lives: opportunity for anecdotal promotion of whatever they swear by for the longevity. Betcha booze has preserved more than one. Whether they have wisdom or only ignorance to share, an unflinching portrait would only have to be honest to be fascinating.
I imagine the job of Oldest Living Human must have pretty high turnover, so there'd always be a opportunity to get to know new folks. If one has a long reign and the material dries up, profiles of the next in line could always be used as teasers for the next season or story arc.
Every show, if it's going to be a hit, should have spin-offs; there's no shortage of potential OLH spin-off potential. MSNBC already has their Lock Up show, how about Oldest Living Human In Captivity? The stories on that one should be enlightening. "Yeah, I shanked another hobo in a boxcar between St. Louis and Memphis for trying to steal my can of beans." Oldest Living [Nationality]. Oldest Living Active [Politician]: there should be plenty of Robert Byrd stories, and Ralph Hall also looks at first glance to be suitably nutty to deliver some tragi-comedy.
Time to polish this idea up and track down Mark Burnett.