FlyFF - Flyff (Fly For Fun) is one of the greatest running fantasy based MMOs.
Realm of the Mad God - Realm of the Mad God is a best online hack and slash video game that includes pixel style graphics.
LaTale - LaTale draws heavily from some other 2D side scrolling video games to provide a great fantasy MMORPG world.
Runescape - RuneScape is 3D Action-Adventure, Massively Multiplayer Online, Role-playing, Fantasy-based and browser-based video game developed and published by Jagex.
NosTale - NosTale (The Tale of Nomads of Silver Spirit) is a totally free MMORPG that includes simple (but beautiful) graphics and also lots of class options.
Dungeon Fighter Online - Dungeon Fighter Online is a Free-to-play, Massively Multiplayer Online, Role-playing, Action-Adventure, Hack and Slash, and Fighting video game created and published by Neople.