Definately going to have to say EverCamp is better, simply because it had be addicted since its release until up to a few months ago, with a few breaks during that time for a month or so long.
The beginning was awesome before it was overcrowded, I remember playing my necromancer before they were nerfed to level 50 in roughly a month. One of the first level 50s on my server (Erollisi Marr

)
After Kunark was released it all went downhill for me in that game simply because the fun had be sucked out of it. I got my character to level 60 months ago, but just wasn't nearly as fun as it used to be. Compared to UO I would have to say EQ owns it. Asheron's call is a better comparison.
Anarchy Online comes out supposedly at the end of this month, I'm hoping that turns into a hit.
Horizons looks amazing but I'm not holding my breath, the project has almost been dropped because of lack of funding and its only just starting..they have a long way to go. If the developers make it, should be amazing
-Judge