Anyone who is going to see this should put in mind that although same universe, this is Korra's story, not Aang's. Obviously a sequel has zero chance at blowing minds as the original does, but setting is different, the time that this takes place is different, Korra's way of raising, and the journey she must take is different. I loved ATLA with all my heart, but I want to give kudos to Legend of Korra for being much more relatable while still being in the magical universe of Avatar.
Korra doesn't get to be adventurous and free-spirited; she jumps into a world where there are constant eyes on her; expectations and burdens a teenager girl should not be facing. The government, the press/media, the public reaction, and ideals of her enemies feels very up to date and relatable; (even though it takes place in a 1920s kind of setting) and this joined with the pressure coming from her teachers, parents and friends are things we face in our time, every day. She tries to be the Avatar while all of this happening. Alongside the actual missions she pursues, they really portrayed her character growth very impressively (she was far from perfect).
This series gives more in depth information on this universe and its origins too, from first Avatar to spirit world; and I personally really liked it. I thought Firelord Ozai was very frightening, but I found Korra's enemies to be way more terrifying to face. I guess one major difference between the two series is that ATLA gets very cheerful and funny most of the time, along with the emotional and super cool action sequences in between, while Korra goes on a more serious note in general even though it also has some funny scenes, it is never as cheerful or light-hearted. I guess that is because Korra herself is more serious in nature from Aang to begin with but also average age of all characters and the constant adult supervision they have, it is expected. I think from many perspectives this is a greatly written show.