I'm sorry, but I think you're taking an intensely shallow look at this show if you can't appreciate the amazing things they did with Zuko's character. It's a really impressive feat when a show can make the villain as sympathetic and well developed as the good guys. When the show begins you get a very clear picture of Zuko as a cookie cutter villain. He wants to capture the Avatar, but they don't give you his reasons or motives. As it goes on, they show his past and his search for acceptance and make him more human. Zuko was never really a bad guy, he was corrupted by the beliefs of his people and a search for his father's love. It's when Zuko finally gets what he thought he wanted that he realizes it's the wrong path, and he gives up everything he's worked to earn in favor of turning his life around. I think that makes him an extremely respectable character in his own right.
You say you can't like Zuko because he's supposed to be the bad guy, but then you're ignoring one of Avatar's major themes. Redemption and forgiveness run very clearly through the entirety of the show. Iroh was once a war general, but he turned his life around as well and I'm sure you can't say that you still find him evil. No one is perfect, but Zuko's character arc and eventually redemption, in my opinion at least, played out perfectly and were one of the show's most impressive achievements.