lvl up system? be more specific =p
you want free ones or are you willing to pay too?
www.tibia.com - free 2d mmorpg, easy to level/get rich, and very nice community on most servers
www.mapleglobal.com - free 2d mmorpg, very nice community, simple stat/skill system, and alot of quests
check out the mmorpg lists on the free mmorpg section =p