Sasuke is the most unrealistic character in Naruto you goof. Not saying I don't like his character, he's in my top 5 fav, but the majority of people do not and would not relate to him. They would more so either "think" they are like him or envision him as an alter ego of themselves that we at times want to emulate.
1. You're more likely to find a person that generally care and have some concern for weaker/less fortunate people, insecurities and personal image to an extent, rather than someone who truly just doesn't care about anyone but their own. Very few people have the kind of "don't care" attitude Sasuke has. There are, however, plenty of wannabe badasses that would like to be like him
2. Everyone "is loyal when they want to". Even if you have loyalty for no one but yourself, that just means you don't want to be loyal to anyone else. That wasn't a very good point
3. People die and people kill everyday, true, but most people wouldn't devote their entire lives to revenge, even if someone kills a loved one of theirs, as most people truly just don't have it in them to be killers. Most would want to, would definitely think about it, but few people would follow through. That's why we have court systems, so you don't have to kill them
In truth dude, there's a reason Naruto is a more typical style of character you will find more than Sasuke. He's more relatable. While no one is perfect and many people have some sort of dark side to them, people are typically nice, even those that try to pose as otherwise, have dreams, and generally believe in themselves and will keep trying even though some will tell them it's obvious they should quit.
That's what being human is all about. I bet you've got some dream you want to accomplish for yourself, and you've probably at one point doubted yourself (Naruto trait btw), but I bet you still secretly desire it. Honestly man people admire Sasuke as a character, but only internet thugs and fake tough guys think he's a representation of the real world