Its very unique and has large target audience. To do that successfully is a challenge in itself. In my opinion it did do that quite well. Though as HB13 pointed out it has the 1 to 1 episode to story ratio which has its positives and negatives. But by allowing both people who love anime and people who dont to enjoy watching it automatically makes it a 'good' series. When you add in the artistic style and approach it takes I think you end up with a great series with a large chance of success in todays industry. As for calling it the best.... i dunno about all that