Ehm the ones that are free aren't great ( in my opinion) And do you mean free to play? or were you don't need to pay per month? If so, Guildwars was my favorite next to WoW. The only negative part of WoW is... you need to pay each month >_> But It's worth it!
Goodluck with your search
Here is a link where free MMORPGs are listed, I'm not sure if all the MMORPGs are listed here: http://www.freemmorpglist.com/