Id say give SWTOR a go, It is a F2P game now, but it was developed as a AAA release and it shows in a lot of ways. The fully voice acted character storylines are (for the most part) superb, and the art direction is fantastic throughout the game, with tremendous attention to detail.
Additionally, you can play it fully single player if you wish, just interacting with other players for Flashpoints(dungeons) which are fully optional, and the Galactic Trade Network (GTN), which is the Auction house. There are 8 class stories to play though. This is how I play, and I enjoy it a lot.
It can be played F2P, but Subscribe for the best experience imo.