I think the main problem is that the UT3 Community is too small. The main reason is that the most UT2k4 Pro's aren't good in UT3 so they think:" why should I play UT3 then?!
"
Back to the servers: Like Splitter said: jolt.uk , warhouse are the best vctf servers.
There are some good (T)Dm servers too, like Flashkick, Tetris, Aimless Gaming etc.
And since Raptor Squad bought a CTF (I definitely like CTF) server, there are many players too.
Warfare: Raptor Squad Server (with many Problems, but it got better the last few days), the rest are only Titan Shit Servers
Greed and Betrayal are dead imho