My brother is addicted to
Runes of Magic. It's one of them item-shop types. It looks like a WoW clone.
As for something I can't really recommend, since it's been so long since I played I'm not sure what's "on the scene", Shattered Galaxy:
http://www.sgalaxy.com/
I realized someone posted a game made by Nexon. That same company made Shattered Galaxy. I remember playing Shattered Galaxy open-beta several years back. That game probably "ruined" [but it was good] my childhood for 2 years.
It's like a Starcraft MMO 20 vs. 20 battles, minus the buildings. You only get to control up to 12 or so units maximum in a battle. You can level up your character, allocate stat points, e.g. one stat will allow you to add an extra unit in battle, or another stat will allow access to better equipment for your units. Free accounts are handicapped.
The main idea for offensive team-play is to try to keep at least 1 unit on the "POC" (it's like the extraction point) for an x amount of time. For defense, well, the defending team just has to make sure they kill any units that's standing on the POC-area.