Sid is awesome. Here you have him, he is know to be really hot, and dominant. Sid is powerful - sit in a great place of power and mainly have the chance to get any chick he likes.
He is also known to be very sexy.
Since Sid is someone like stated above, people use it to describe something awesome or an awesome/sexy/cool person.
Melanie: I banged Sid yesterday. It was something I will never forget. Wonderful.
Ann: I'm so jealous!! You are lucky to have a sexy Sid.
Mike: He has a lot of girls, you know.
Melanie: SHUT UP, VIRGIN, JUST SHUT UP!!
Sarah: Who is that guy? I never seen something like that... He's so sexy, I just want to blowjob him right over!
Liza: He must be a Sid.