As for Civilization II - it sucked hard and if anyone feels insulted about this claim, then they really have to sit down and shake their brain box to remember if that Windows monstrosity of Civilization II was really that great. Sure, videos of advisers was new technological advance, which very quickly became nuisance and then were turned off. Music was initially great, but after a while I had to play Civilization II without it, unlike Heroes of Might and Magic II, which had the greatest music and was proper full screen game for Windows(and DOS!!!). Not to mention, that there was great strategy game of Master of Orion 2: Battle of Antaris. And then there was a Civilization clone - Master of Magic - with had a very successful following as Age of Wonders. Anyway, I can still enjoy first Civilization(even with that nasty bug, that glitches Earth map in late game), because of Genius simplicity of a game, but can't say the same for Civilization II even if I had fun when I played it, because usage of Windows GUI in Civilization II will feel outdated and very unappealing, which only later Civilization titles fixed.
As for Alpha Centauri - it was not as widely available as Civilization II and technical specifications were ahead of most of PCs, when most of them were not powered by latest Pentiums. That sucked, as I really wanted to play that game(hence the discussion about greatness is more limited, unlike about first Civilization), but by the time I was able to get a hold on it, it was already outdated(and unplayable due to Windows compatibility and color paletting issues!!!), compared to other games that were released at that time.