If you never played Demon's Souls on the PS3, I suggest checking it out if you have a PS3. Other than that, there's nothing else quite similar to Dark Souls. You might consider looking up the King's Field and Shadow Tower (Abyss has a fan translation, it's nice) games, since they are by the same developer, but even these are very different (it's interesting to see the developer's relationship with RPGs, though)