Manufactured goods, population, and land area in that order.
As I recall, some of the the other variables are not measurements in absolute terms but ratios. This means if i capture a couple of poorly developed AI cities then my values for literacy, life expectancy, etc will fall even though my civ has clearly not declined in absolute terms. This makes these numbers less dependable yardsticks.
Manufactured goods is the most fundamental measure. Whoever can produce the most units is a long way towards winning the game.
I view population as a long term forecast of the manufactured goods. If I fall behind in population for too long then it's inevitable that somewhere down the road the enemy will overtake me in manufactured goods as well.