Personally, I think Light because he's so smart but there are a lot of other good ones out there

I feel like the creator made light act unlike himself in the last couple episodes (stupid) so that the anime would have an ending that the majority of people would agree is the “right” ending. I think based on how he was throughout the anime it should not have ended the way it did, but that’s just my take on it. (A little off topic but I wanted to share my cup of tea)

It SHOULD have ended with him dying of old age, giving his notebook to a successor or something.

Best Anime Protagonist is "Sword Art Online: Abridged" Kirito, tho I dunno if that counts.