It had an interesting concept, great animation and very good characters. Which remained great mix of a highly promising anime.
That being said, as episodes grew, it was somewhat disappointing. As the oh-so-good concept merged with not-so-interesting portions. It felt stretched and it's never a good thing when you feel that 25 episodes (imo, the ideal no. of episodes in anime) feel ill-paced. Not to mention, that the plot also had many plotholes and fanservice to cover those plotholes.
The silver lining is the sweet romance between Kirito and Asuna. And that's also the main reason of its hype. The romantic pair is really loved by those mushy otakus and this created lots of hype. Some even comparing this love story within a fantasy concept to epic animes like Steins;Gate - where the romance is not only better in my own taste but it's plot/concept execution are millions times better than SAO.
Overall, it's worth a watch for some factors like romance/animation/initial concept. But it remains nothing groundbreaking. I'd give it a 6.5/10 which is a rating that can be classified as passable in my book.
As far as comparisons with Ao No Exorcist and Shingeki no Kyojin are concerned. Well, it's a simple comparison due to hype. Ao No Exorcist was one of the most anticipated and hyped animes of 2011. It wasn't the best of 2011 nonetheless. Sword Art Online was arguably one of the most hyped animes of 2012; if not ever. But it was far from the best of 2012 imo once again. As for Shingeki no Kyojin, it's the most hyped anime of 2013. Credits where it's due - till now, it's the best anime of this year though there remain other promising releases that may top it off in this year. But Shingeki no Kyojin is not the best anime of all time nonetheless - that's just overhyped opinion.