There are some objective measures. Although they're somewhat problematic, Steven Pinker presented some relevant stats in his recent book (I think it's called Enlightenment Now). Then there's the leap in technological empowerment that's enabled us to go to the Moon and Mars. That kind of progress is still partly subjective since it's subject to the goals that technology helps us achieve. But there are likely some universal goals that spring from our species' existential condition, and some societies are better at achieving them than others. That makes for a partially objective measure.