Stewie - Evil Baby Genius who has a British accent and hates his mother, in later seasons his character trait is still like he is a genius but they replaced evil with like gay
Peter - Loving Family Guy who isn't really smart but does the best he can, ever since like Petarded i feel like they kinda just focused on the stupid part
Brian - the straight men who was sarcastic whichover time just became to express the writers political views
like as much as i love brian(which is kinda obvious) i think his personality has became the most downgraded in the show
he's also like a chick magnet, literally there are mulitiple episodes about him being in a relationship with a human
Cleveland has actually gotten a upgrade which is rare i guess?
tbf they did give cleveland his whole show where he was able to really build out his character