Our servers just started a few months back so the popularity still isn't high but our Oman does rather well about 75% of the time have at least 20 people in it.
24/7 Oman by EoT.
We also have an Infantry Only server, but the name and map changes quite frequently as we change it if we feel we want to play a different map.
We also admin a very popular Karkand server...
24/7 Infantry Only Kark by GODS
^ That server is full almost all the time, its a 42 man Karkand, EoT. (My clan) and =GODS= are really close so we admin each others servers.
Both our servers and the GODS karkand server I am 100% sure Ranks up, as I have earned about 2,000 points within the last week or so.