Typically, I'd call it Cruiser Online for the Fed side, and Bird of Prey Online for the Klingon side.. Because on average I see more Cruisers and BoPs then anything else..
I agree. If you look at more than just the PvP community there are a lot more cruiser captains than sci or escort captains in this game. Just sit at ESD for a while and tally up what you see LOL. As someone said earlier this is greatly due to Icon status. The most popular ships in game are the most Iconic ones, like the Def-R, Intrepid, and Soveriegn. When the Ent-F is released Cruiser count will multiply exponentially.