I don't think the OP applies to me 100%, I don't think everyone are selfish, but I do feel somehow detached because I just don't have the enthusiasm to care about things other people do.
I just don't have the same emotional attachment as some of the people, they're so excited over a film, a video game, they might appreciate what they're seeing, or they could feel badly offended because someone is talking **** about his favorite song.
Watching people on the street being so excited with their friends, they don't care about what others are just there staring at them, and they would be so mindlessly happy that they're not even aware they bumped into me or almost poked my eye out with their umbrellas, they talk so loud as if they're the only people on earth.
I don't really hate people, good for them that they're happy with their everyday life, I would too if I were them, but I feel hollow watching them.