No, CiV is not replayable. You can only pretend it is. Civs do not differ much, and actually there is usually only one best way to win. (going wide and spamming GSs)
Of course you can have "replayability" if you play prince. Spam wonders, build mounts, adopt commerce. But at deity and especially in MP you wont survive if you do this.
Apart from a lot of minor and moderate balance issues, I think that the key problem in lack of replayability is that civs are too generic. I dont propose anything like starcraft, but several major UAs with few minor UAs (several UB/UU/UIs would be good as well) per each civ could lead to much greater replayability.
There's a good argument to be made that semi-tall/wide empires are hands down the best way to do well in Civ5. There's a good discussion going on in the ideas forum to allow for more varied 'good' empire building.
But most of your points seems awfully general and inaccurate. People in this thread have posted wins with small empires on high difficulty settings.
and the comment lack of Civ uniquement is weird. UA's and 22 UU/UB or UI give the Civs plenty of variety. I tried out Bablyon recently and it's a completely different early game than the other Civs. Early UUs of Babylon even make Honor SP worthwhile for culture farming.