Some very minor spoilers ahead, but nothing major to the plot of GTA 5!
What sane person could ever identify with Trevor Phillips? He's a balding, creepy-eyed goon, liable to ruin a stranger's life if he doesn't outright kill them on the spot. Trevor's a modern-day Caligula, prone to violent outbursts in one moment and deviant sex acts in the next, oftentimes combining them into an extravaganza of obscene debauchery. He flies in the face of every Grand Theft Auto antihero that's come before him, what with his complete inability to control his hedonistic urges in the presence of criminal kingpins. And yet, in creating Trevor, Rockstar has finally crafted a character who's in line with the spirit of the GTA franchise.
Think about the way you play GTA--particularly the first time you ever laid hands on it. Did you purchase a car, drive on the right side of the road, and yield to pedestrians? No. You carjacked some poor schlub, then started doing 90mph on the sidewalk, mowing over civilians like weeds in a yard. People have a pattern to how they've christened every entry in the GTA series: find a save point, then wreak utter havoc. First, you shoot random civilians to gain some Wanted level. Then, perhaps after activating some GTA cheats, you murder the first-response cops that show up. You want to see how many Wanted stars you can rack up before you're finally shot down in a blaze of anarchic glory.
That's part of the freedom of GTA's sandbox: the power to be as notorious a criminal as you want. Problem is, no one would ever actually act like that--least of all GTA's protagonists. Niko Bellic's immigration was meant to wipe his moral slate clean. Tommy Vercetti wouldn't piss away his budding drug empire in a down-and-dirty firefight. Carl Johnson just wants to keep his friends and family in one piece. Claude Speed might be a psychopathic mute--but he's barely a character at all. So when story-progressing missions force us to perform horrible acts of violence, it doesn't feel plausible. There's a palpable disconnect between the words and actions of these street-smart up-and-comers. None of these characters could realistically have an honor-among-thieves conscious in a cutscene, then gun down hundreds of living people in the subsequent mission.
But as Trevor, it makes sense. He's a wildcard; a bipolar maniac that will act on any erratic emotion. After falling off the radar following GTA 5's opening vignette, we get the pleasure of reacquainting ourselves with Trevor when he's balls deep in another man's meth-addicted girlfriend. And what does Trevor do when said man gets upset at this affair? He stomps the guy's head into a pink paste with the heel of his boot. It's believable that Trevor would start a shootout on a whim--hence the various Rampage missions scattered throughout Los Santos. There's no behavioral dissonance when he runs over a bystander and doesn't care. He's the kind of lunatic who would crash his car at high speeds just for fun, laughing as he flies through the windshield and skids across the pavement. Everything you do while playing a GTA game lines up perfectly with Trevor's personality.
Compare him to Michael and Franklin. Sure, Michael is in definite need of some anger management--but in his heart, he's a level-headed family man who's addicted to the thrill of thievery. So why would he slaughter local policemen when they pull up to the scene of a heist? Franklin wants a better life for himself, even if it's funded by crime--but he's constantly criticizing Lamar's affinity for glorified gang violence. Michael and Franklin steal cars and shoot cops as the regrettable means to a morally defensible end. Trevor does these things because he feels like it.
It took 16 years and 12 primary entries in the series, but Rockstar has at last created a character that aligns with the player's modus operandi. It's not that Rockstar thinks its audience is full of gnarly, deranged psychopaths--for satire on the gaming community, look no further than Michael's son Jimmy. Trevor's existence isn't a commentary on any group of people--he's just the first logical fit to the way people have been playing GTA games for the past decade. He lives like his actions have no consequences, because this is a game, and they actually don't.
Once you come to terms with that, you'll find that it's a lot easier to like Trevor. Yes, he's constantly abusing the only people that care about him--but he's the product of a rough childhood that left him with severe abandonment issues and an inclination to distrust anyone he meets. Trevor's always boasting that he's the only honest person in a place like Vinewood, and in some ways, he's right--he'll never hide behind a façade or be afraid to speak his mind. Trevor doesn't like bullies and phonies--and when he's not overcome by rage or high on methamphetamines, he really doesn't seem to like himself all that much either. He has the brain of a child and the neural synapses of a drug fiend, so forgive him for some destructive temper tantrums, indecent exposure, or unsolicited proclamations of true love every once in a while. Trevor just can't seem to help himself.
So the next time you hire a hooker in a GTA game, then murder her post-coitus to get your money back, ask yourself: Does this make any sense? Would my character actually do this? As Trevor, the answer is yes. Anyone else is just the puppet of your morbid curiosity. A world full of Trevors would be an awful place to exist, full of barbarism and random acts of sodomy. But as one of the stars of a Grand Theft Auto game, Trevor's the perfect fit.