If the database on here is anywhere near accurate then Odin is the most populated server. You have to realize that the game isn't the same as it used to be and you don't need near the people to do just about anything anymore, in fact a lot of content can be solod, or trust solod.
I know the game has a lot of solo content, I took my newbie char f from r1-r5 alone in the past couple of days and am now doing Aht Urghan all the while leveling/farming/etc and considering redoing CoP soon, so I'm not really looking for groups yet (though it would be a lot more fun....) but I am looking for people to talk to and befriend as I'm remaking this char. If we can do stuff sometimes great, but at least some company. The whole charm of this game was shared adventures and well...my trusts are nice and all but not too talkative.
Odin is populated....by mules and JP players. I happen to live in Japan most of the year and speak Japanese fluently but I'm American and I'd prefer to play with the NA/EU community.