Trevor was the better character in the game. Except his for bisexual bullshit. But yeah he was pretty much like an animal. Which apparently means he would screw anything and he didn't care.
He was way more interesting. Michael wasn't bad but Trevor pretty much stole the show from Michael. Trevor provides people with a power trip fantasy. Minus the drugs and bisexual garbage he is pretty much a badass. He makes Michael look like a whiny bitch.
As for Franklin? Franklin is just typical nigger shit. Though he was less niggerish than what went on San Andreas. But it was still pretty much some ghetto BS. Basically Franklin is the video game version of the "gud boi". He jus tryna get his life togever. To make him more endearing to white players Rockstar actually had him doing that. He gave up his life of petty nigger crime to work for a crooked foreign car dealer. He then moved up the crime ladder with Michael and Trevor. So he never really gave up the criminal life. He just engaged in different crimes.