there are very much games that are similar to diablo,

there are:

Maple story but i didn't like it so much

Ghost online but it is to much like maple story so i didn't like it

Archlord i played it for a few weeks but it gets boring after a wile

Dungeon runners is a good game but like archlord it gets boring after a few weeks

2moons is a good game and i like it but there are too many players and not much servers so the game get stuck

Shaiya is a good game and i still play it,for now it is the best game from the list above i played.

but the best game i played is the original diablo 2 LOD

also a good game i played is titan quest but i lost the CD-Key so i cant play it anymore but it is a good game.