I'll do actors and characters because for me they don't correlate. lol
Actor: Blake Berris (Nick) but I hate what the writers did to Nick. I'll never understand why they couldn't have done the first half of his return from prison story and then do a captivating storyline about mental disorders or show his recovery in therapy. I don't even watch General Hospital and I know they did the prison rape storyline way better. He's my favorite actor because partly for attachment factors. Nick is the only character I know his entire history, because he entered the show completely new, then I stopped watching when he left, then started again when he returned. I've also seen Blake evolve as an actor and he has this heart and passion with his acting that I'm drawn to as a writer. On a personal note, a friend randomly met him last month at a film festival (I found out after, and she didn't know I was a fan until after) and she said he was beyond nice so that makes him more of a favorite.
Actress: Arianne Zucker (Nicole) but I don't like what they're doing with her character right now. All her character relapses are annoying me. They seem to be used to justify that she will never really change, which I've seen a lot of Nicole's history, and I think she's evolved enough to not be so desperate to keep a man, or at least learned from her past. So I get annoyed when they create these actions just to make her unlikable or someone you can't completely root for. Ari Zucker is my favorite actress because even when I should hate Nicole I don't. She always adds a sincerity to the character that doesn't work with other characters. Sami, Nicole, and Kate have done really similar actions but Nicole is the only one I never hate, despite the insanity and maliciousness behind it.
Current Characters (those still on the show/if I got into all time favorites or those no longer on the show it would be a lot different and too long, though this was already way longer than intended. lol.)
Sonny: there is something just so wonderful about the character. If there was ever a character who just has this quality that makes you like them, it's Sonny, which is probably due to Freddie Smith's acting. He's probably my second favorite actor, but we'll see. I just want him to have a storyline beyond hating Nick, trying to save Gabi, and being a husband to Will. He's great with everyone he works with (I loved the Victor and Sonny scenes a month or so ago!) so he needs more interesting solo storylines.
Lucas: But right now, I'm kind of annoyed he didn't stand up against Kate/protect Sheryl. There were some questionable Lucas moments in his history, but I think he has a mixture of Sonny and Nicole qualities. He has a natural charm and even when he does bad, you still kind of like him. The only scenes I like with Sami are hers with Lucas. In my mind, they'll always belong together even if they never are on the show again. It just works. But Lucas also works with any love interest. I actually really liked Lucas and Chloe, until that got messed up. And I like Sheryl and him. The only questionable relationship with Lucas for me was Nicole. Something didn't click, but it might have been because it was around one of Lucas' 'villain-type arcs.
Stefano: I honestly don't know. He's just a fun villain. It's what I hoped they do with someone like Nick, another missed opportunity. I actually enjoy when he outsmarts people, especially EJ. He brings a hilarity to a character you should really despise. In the past, his scenes with John or Steve used to be some of the show's highlights.
Ciara: I'm a fan of her sass. She's going to be such a teen rebel.
Justin: I just like the characters' spirit (though we rarely see it). Justin and Sonny definitely seem like father and son, that's one of the few parent-child characteristics (only other one is Abby and Jen, but not in a good way) I feel the show has gotten right. I can see clear overlapping traits, which is probably why I like them both so much.
Growing on me: Hope, Aiden, JJ and friends. Aiden because I think the actor is pretty good and I feel like if his character ever gets fully flushed out, he could be really intriguing. Hope I've always been kind of a fan, but she hasn't been getting much to work with recently. Paige and JJ's storyline reminds me a little of DOOL when I first started watching it, so I could end up liking both characters if the writing gets better.
Other than those, right now all the other characters currently on the show are just not working for me. But that could change depending on if the writing for them gets better...I blame the writing overall. I think the current acting team is actually fairly good, but some of them/most get nothing to really show their talent or even make you care about the character.