Sword Art Online is turning out to be pretty good. It's one of the few from this current season that I'm finding myself looking forward to the most and is already holding my interest more than Accel World is, which is by the same author, not to suggest that the latter is boring me. I suppose it's the sinister premise, of which I like and find quite original, of having people play the game against their will and at the expense of their own life in reality if they lose. I also prefer the characters in that their roles are less contrived than in Accel World. I also prefer the protagonist, partly because he's more ordinary looking and in keeping with everyone else, but also because he's a lot more logical and seemingly experienced.
I haven't read the light novels of both, but according to my friend Kiki who has, both are set in the same world/universe, only that Sword Art Online is a few decades earlier, which makes sense given that the technology used to play the game is less advanced than that in Accel World. I do have to wonder whether there'll be any parallels between both, and whether the game in Accel World is by the same developer/creator, which would make sense given the secrecy surrounding it. Would be interesting, in any case.