Agreed. Bill Clinton credibly made the same claim in 2000 that were he eligible he could have won a third term.
He might have won more than that. It is not out of the realm of possibility that Bill would have been re-elected again in 2016 for a 7th term. He would easily have been able to fend off a primary challenge from Obama.
I realize this is pure speculation, but Bill Clinton underwent quadruple bypass surgery in September 2004. That could not have been allowed to happen had he been in the middle of a re-election campaign for a fourth term. Had he delayed the surgery to keep things quiet until after the election we might have had an even closer FDR parallel.
In any event, even without term limits Bill would be well past his "sell-by" date by now.