1. Johnny Klebitz - The one I relate to the most on a personal level. He was so black-and-white on the outside yet still colored on the inside. Seemingly a very coldhearted, tough and fearless character to outsiders, but that is just his misjudged outside and in reality he is a loyal "brother" and companion. Playing as Johnny K and hanging out with the good guys in the Lost MC reminded me so much of myself and my brothers - a closed circle but also an unbreakable one.
2. Niko Bellic - More or less tied with Johnny as the #1. I always thought he and Johnny were a lot like each other, except they had different backgrounds and styles. Niko was probably somewhat more colorful compared to Johnny, despite also coming across as a coldhearted killer (in most cases anyway). I really connected with Niko and his story felt like he was initially a good guy turned bad by his own friends, and to some extent his native country's government and whatnot as well.
3. Tommy Vercetti - It's been a long time since VC so it's hard to remember everything, but I do remember thinking Tommy was being very intimidating and commanding. A fearless man who'd get things done, for good or bad. I really enjoyed playing as Tommy back in the days of VC.
4. CJ - A somewhat down-to-earth kind of protagonist. He was good at being a thug but also striving towards not being one. With that said, I think he could sometimes come across as whiney which kind of annoyed me ... a lot.
5. Victor Vance - Possibly the most honourable protagonist. I thought he was a refreshing protagonist at the time but unfortunately I don't remember much else about him or VCS.
6. Claude - I thought GTA III and the 3D era were so cool when they arrived. I was just a kid at the time but I remember thinking that Claude looked like a badass. These days I like him more for being a mute. That way he can't be as annoying as the remaining protagonists. (lol)
7. Trevor Philips - Interesting character to say the least. I like Trevor, apart from killing Johnny (f*ck you R* for that bullsh*t btw), but I always had one problem with him. To me he comes across as more of a supporting-type character or even a main antagonist. I think it was the wrong move to make him a protagonist. It would've added more mystique to his personality if he'd just been an NPC.
8. Michael De Santa - A typical middle-aged drunk dad who's still stuck in his teenage dreams. Not quite what I regard as GTA protagonist material, but whatever. It's more or less the same thing with Michael as with Trevor - he should've been a supporting character instead.
9. Franklin Clinton - How do I best describe my opinion about Franklin? Well, he's like a CJ lite. Rather futile and overall underdeveloped. Meh.
10. Luis Lopez - Ugh. I just hated him. He's the epitome of what kind of people I tend to despise. It's something with his attitude and way about things. Just no.
11. Toni Cipriani - The only thing I remember about Toni at all is thinking he was piss boring, both as a supporting character as well as a protagonist. That probably sums it up perfectly anyway.
I don't recall much about the rest and/or I never played as some of the remaining protagonists at all.