Shit happens. Sasuke, however, decided to make things worse for others because of the emptiness in his heart. A lot of people see this as selfishness, and they're right. It is selfish. But people who have been in a hole like he has understand his position. They can compare themselves to him, and that makes them like Sasuke, but not necessarily like his decision-making. That's my situation with him. People also think that he is becoming strong way too easily and without effort..for some, they also agree on this for Naruto as well.
Most of the reason, however..Is the fanboys and fangirls who obsess over him xD
But joking aside, Sasuke has likable traits as well. He cares about his brother and family, he's strong, he's smart, the list goes on. I just think he's less likable in Shippuden for being such a jackass.