Sword Art Online is part of the isekai genre. I made a post about the genre (https://steemit.com/anime/@medicinemerchant/inside-isekai) where I briefly go over the history of isekai and what legacy each period has left.
When it comes to how good SAO is compared to other isekai, I would have to put it towards the bottom. There is a lot that can be done with the idea of going to a different world or being trapped in a game and SAO didn't begin to touch the surface. .Hack//Sign seems to be a big influence on SAO and it goes a lot further into the mentality of a character that cannot log out of a game.