Who would be a good candidate to become the main protagonist lore wise?
Note: I said protagonist not hero, doesn't have to be a good champion, villains are allowed too. I just wanna hear what other people think?
I always thought Ryze as a main character simply because I see Riot trailers and picture hinting this.

Good question. I would say, possibly, Jax, Jarvan IV, or Garen, just because of their lore. Jax is the "best" champion, Jarvan is the Prince of Demacia, and Garen would be like call of duty- Not the head of the army, just another member.

Teemo the little rat shows up every were. I hate him so much

I would say Jax for his effects on the league. If not, Jarvan IV or Swain, given that they lead the largest city states and held power during the incident at Kalamanda.

Jayce

I'm extremely grateful there is no main character in the league, but I'll bite.
Jax Can't be the main character as He has no where to progress He's already the best there would be no story. Jarvan is a ******y prince. Garen Could be a main character if we assume a Noxus evil Demacia Good Binary, but this leaves out all the other city states.

For the current state of story telling, I have the misfortune of saying the most probable main character, In his youth and his progression is Unfortunately Ezeral.

Jax would make a better rival to the protagonist. He's definitely to moral to be the antagonist, or even on the evil side of the spectrum for that matter, but he's most certainly no main character.

Evil would just be a take your pick situation. you could have a really good plot arch or saga with Fiddlesticks as the main evil. Noc, Veigar, Singed, Shaco, etc.

Akali, Kennen. and Shen would make great good guys, but not the main character. They are more like enforcers for good and don't seem to have enough depth to flesh out a protagonist.

Twisted Fate would make a great "han solo" character.

Lee sin would make an awesome protagonist. Plenty of depth and back story, room for growth, troubled past, etc.

Vongeo is right though. Ezeral does, unfortunately, make for the most fitting "main character."

As much as I hate Teemo, he also wouldn't be bad.

Cho'gath. Nuff said.

Kassadin, we could see how he fights the void outside the arena >

Swain.
Because he's probably going to be in the midst of things, whatever the event is.
And because he isn't that ''good guy''. What can I say, I like anti-heroes as main characters.