If you put it that way, civs3-4 have 1 way to play for ALL civs. Actually Civ5 civ abilities differ significantly. For example: - Poland have very generic bonus, which doesn't restrain gameplay at all, but allows strategies you normally can't use, i.e. by adding 1 more policy tree. - Huns let you try otherwise completely weak approach of early conquest. - Indonesia ability encourages island settlement, but otherwise it fits all strategies. And so on. So yes, unique Civ allows more different strategies and more replayability.