[quote=@DarkwolfX37]
<Snipped quote by souleaterfan320>

Ew. No it's not. There's no way SAO replaced Bleach or Naruto. How are you defining big four?

<Snipped quote by Nimda>

Well for one, it's really similar to .hack, and Log Horizon is the same thing but done better and with a more psychological viewpoint. 
Secondly, a LOT of people dislike it because of how much wasted potential it had and how it's like, THE most generic shounen anime of all time. Plus, having the main character be a mary sue and having the best character get shoved away halfway through pissed off a lot of people who were fans until then.
Then there are the people who look at it analytically and wow does it not hold up under scrutiny. 
And lastly once people realized that it was just a power fantasy anime, they moved on to better power fantasy anime like To Love Ru or One Piece. 
[/quote]

Bleach, naruto,one piece, SAO. Fairy tail is pretty much tied with bleach and one piece, though.