Era spanning games as which civilization? That's a broad question. If we are just talking in general, I would say the biggest difference between "short" games and "long" games is in the former, you spend most of your time training units, and in the latter, you're actually able to spend more time constructing buildings. With Great People, the dynamic really shifts from always using Great People to bulb technologies, to actually being able to settle/create Great Buildings. And with diplomacy, you go from not really caring about long term consequences, to choosing wars and sides more carefully, in order to not cause too much diplomatic penalties.