Well - from playing World of Warcraft, I'd say it is by far the easiest to get into for a newcommer to the genre that I've ever tried.
It is easy, fast paced and penalties for dying are very small. This means it is good for newcommers and casual players (or both

).
I've not tried Everquest II myself, because it has never appealed to me for some reason.
However - I have played Dark Age of Camelot extensively and would not advice that game for a new commer to the genre, and almost not to a MMOG veteran either, because it is such a timesink.
EVE-Online is another I've played for a while and is good if you are more into space exploration type games. However it is hard (well was when I played it) and full PvP which means you can die very often.
But there are many others on the market.
Star Wars Galaxies and Saga of Ryzom I've only tried back when they were in beta, but didn't find them fun enough for me to keep playing, so I can't advice on that.
City of Heros, Lineage 2, Ascherons Call 2 (spelling?), Guild Wars, Anarchy Online are also all MMOGs... so there are plenty to pick from
