What is this soccer you constantly talk about? Is it another american sport? why don't you play football like in europe?
On topic: it will be very interesting to see statistics after the next patch...i bet it will rise again!
Moreover, if i understood well, the stats are "current players". I don't know for you, but i don't start to play civ if i know i don't have at least one or two hours of play before me (and sometimes an hour is not enough for me to start playing). whereas other games are good for less than 1/2 hour sessions...
Maybe at the same time there are less people, but if you count the different accounts on one week or two (there are week when i can't find enough time to play), there may be much more people. See what i mean?