Legend of Korra-Good, not great.
Avatar the Last Airbender was a great show. It was a wonderful story with fleshed out characters, terrific pacing, beautiful art, fun action, good humor, and a great world. It's hard to top that.
And Korra...doesn't. It's certainly good. It has decent humor, some different but still good action, even better looking art, and some fun characters. It's just lesser in degree. The problems come in the story, the characters, and the pacing.
The story had quite a lot of potential but dropped too much of it along the way. The Triads disappear after episode 3 or so, we get one episode of oppression for non-benders, Tarlok defeated far too quickly, and overall Korra and several characters have bad development.
Korra as a character is very well designed for a season that questions bending vs nonbending. She's probably my favorite character based purely on design but her arc just had a rushed ending. Bolin was fun but ultimately had nothing to do. Asami was probably the best of the team in all honesty. As for Mako...he's a mess. He has a simple character arc(he goes from not liking Korra to gradually loving her) but it's so poorly handled. And it takes up way too much of the screen time. Limited word count prevents me from saying too much but I thought he was dreadful. Other characters like Tenzin, Tarlok, Amon, and Lin are fine but some are not given enough to do while others are disappointing in the end.
But the big issue is the pacing. The first four episodes are well paced. After that it kicks into way too fast. The romance takes up a whole episode and Bolin relegated to background. Then Amon blows up a building, declaring war on the city. Then it's revealed that Sato is a bad guy, Asami joins the team, and then the rest of the Krew live with Korra. Then we get Team Avatar, oppression, breaking the team up, a big fight, and a good twist. And more keeps coming at a speed that you can't take it all in. The finale especially is hilariously bad at it's pacing.
Overall Korra is good. I've heard people say it's better than the first season of Avatar but I disagree. I'll take the season that takes it's time over Korra any day.