6. Star Wars: The Old Republic
Star Wars: The Old Republic is the continuation of the Knights of the Old Republic series of role-playing games by BioWare. SWTOR features multiple independent storylines based on the character class you choose to play as. Very much like the singleplayer games, you get to choose your dialogue options and even recruit NPC allies to support you in battle. However, unlike its singleplayer counterparts, each character class fits in with MMORPG mechanics of healing/DPS/tank and the game must be played cooperatively if you wish to get the most out of it. SWTOR is free to play and its story can be experienced to completion without you having to pay a single cent, although you'll want to pay to get more out of the experience.
