Likable and realistic? Your joking right? Light is an idiot douchebag who thinks he's a super genius who's going to rule the world as a god. Oh yeah, also he's attractive...and good at sports...and good with the ladies and....well he's pretty much good at everything, especially being a twat.
L is a teenager who is smarter than everyone in the world except for Light with whom he is equal.
Misa is dumber than bricks and it just goes on and on, I found the regular detectives to be the best characters in the show (though really I didn't mind L and Near I suppose)
Sorry to say but likable and realistic aren't the first words that leap into my mind when I think of Death Note characters
I watched AND read the entire series through, I gave it plenty of chances because I had heard such good things and while I found the manga was at least okay, the anime is just downright EMBARRASSING to watch. Like, my god the montages of people dying were laughable and ridiculous it was really overdone, with the dramatic music and the overemphasized pen strokes and occasionally even more ridiculous things like that stupid potato chip scene which I personally think is the dumbest scene I have ever seen in an anime in my entire life. I understand that they were trying to convey that Light's feeling of power while writing the names down, but it still occurred to me as over the top, but not really in a good way.
But the WORST thing about Death Note, is that it pretends to be a thinkers anime, this really annoys me, not 5 seconds can go by without Light or L explaining what the hell it is that they're planning, or what they just did, or what they're going to do, or what they think the other person is thinking. This is NOT good story-telling, This is spoon-feeding. The whole series' is like that one scene from The Princess Bride with the poisoned goblets, only instead of realizing how ridiculous it is, they take it VERY VERY SERIOUSLY. I understand that some of the scenes of exposition are necessary and that's fine, but I think the whole series could have greatly benefited from letting the audience figure out what was going on, instead of flat-out telling them, considering that the series has a horror-like aesthetic I think an air of mystery could have really elevated the whole experience and indeed made it darker and vastly better. I'd even go so far as to say that the show would probably been a lot better if L was the Protagonist from the start and done from his perspective primarily, while only switching to Light's perspective when necessary.
Though to be fair, as the series went on I do feel it got better, and I actually like both the ending in the manga and anime, but overall I certainly could live without Death Note.
Also Light is a twat.