A lot of people accuse Haruhi of being a sociopath, and yes her lack of respect for norms, people, and just basically everything is quite disgusting at times. Though we do have to realize she is the ultimate spoiled child-- the universe spoils her, quite literally.
Because it bends to her will, she has never had to compromise with anyone. She wants to have fun, and she sincerely believes other people are enjoying it too despite their collective groans and whining. But since nobody would dare oppose her, she thinks it's all ok and that everyone is playing their roles. It eventually gets boring, because everything seems too easy.
Enter Kyon. He's the only one that doesn't act like a doormat to her, and actually provides oppoistion. She seems to genuinely want attention from him because of this. Plus you have to realize how the other 3 view her as...
The aliens view her as a key to evolution.
The espers view her as a god who would destroy the world out of boredom.
The Time Travelers see her as a roadblock.
Basically, nobody really sees her for herself. If she didn't have special abilities, then none of these factions would have given a damn about her. So it seems only natural she would be interested in the one that doesn't have an agenda.
And so, Haruhi is apretty damned interesting character.
If only you know who you were.