First, the story. The "high level" plot is not exactly hugely original, sure, and various stereotypical plot devices are employed to advance the story, but below this is, in my opinion, an interesting exploration of very serious themes. It attempts what I think is a quite honest exploration of the psychology and sociology associated with the main premise, that is, large numbers of people being trapped in a virtual world where the risk of death is very real, for very long periods of time. I think the story shows quite a lot of insight into the human mind and is actually very good on this deeper level. So you might say the actual plot is fairly average, but the immersion and realness and exploration of themes is very good. Some of these themes get a bit lost in the latter half of the show, but it had other things going for it by that stage.
Now the characters. I don't know why people think they are shallow. Kirito is again, on the surface, something of a "glove" character for teenage boys to wear and fantasise about begin a hero, but below that we see a lot of psychological development. The scars he suffers from the various atrocities he witnesses were very believable to me, and the bonds he develops with the other characters likewise seemed heartfelt. On the top level, yes there is again a level of pandering to teenage boy fantasies to have pretty girls fawning over them, but the girls are not at all shallow empty characters whose sole role is to fawn over Kirito. They are each very likeable and have complex personalities (though yes it would have been nice to see some of their back stories developed further, since some of them aren't given much air time). Asuna of course one of the most developed, and it is a shame when she is reduced to the damsel in distress since she is such a strong character, but I love the rest of the show enough that I can overlook this cheap shot. For comparison, The Legend of Zelda: Ocarina of Time remains one of my most beloved games despite that it pulls the same crap on Zelda. The development of Kirito's sister Suguha in the latter half of the show was likewise excellent. She has a rough time and one feels all the feels for her.
Finally, the romance between Kirito and Asuna is one of the aspects the kept me glued to the screen, so that I watched the whole series in basically one sitting, though again I was sad that Asuna semi-disappeared in the latter part of the show, though this did make room for Suguha which was very worthwhile. I thought the addition of Yui was a nice touch and that she was a very likeable character on her own, and her presence was important to add the very serious question of how we would feel about a true artificial intelligence into the mix of themes.
As for other aspects of the show, I thought the art was great, and very evocative so far as really imagining what a virtual world might be like, and the music of Yuki Kajiura was excellent for amplifying the abundant feels of the show (though it is not as listenable for its own sake as her score for Madoka Magika).
This was one of the most enjoyable shows I have watched in quite a while, and so for that fact alone I am happy to give it a 10 overall. It's not the biggest win for feminism in the world like Madoka is, but there is more than enough there to make up for it. If you don't like this show and it doesn't make you cry then you have no soul (jk, sort of…).
