Nonsense. Civ4 is far superior to Civ5.
I really don't know how to rank the first four versions. Clearly every one was an improvement on the previous one in some absolute sense. OTOH, the game had to deal with the limitations of the hardware at the time. Did CivI do a better job in this sense than CivIII? I think yes but the question can be argued. CivV was a huge step backwards no matter how you look at it.