@bold- He's definitely in the top 3 most well-written. Kishimoto covered every aspect plus more with this character.
Itachi is probably like 25% of the fandoms #1 fav, and then the rest have him as one of their favs (like in their top ten). Then, there's like a 1% of loons who think he's the worst-written. However, those loons are usually a) People who distort his character (I've shown you screenshots of a certain member's comments who's username starts with S, lol). b)Those who cannot understand his character due to its complexity. c)Those who are jealous because he humiliated their fav in some way or another (so some fans of Sasuke- mainly the hardcore ones, some Deidara fans, some Oro fans, etc) and then d) Some people hate the Uchiha clan as a whole (one of my friends does, lol. She hates the way they took over the series. She hates every single Uchiha introduced bar Itachi and Izuna. She's indifferent to those two).
I laugh alot anytime I see a negative comment regarding Itachi. Mainly because, if anyone writes a negative comment, they ignore key facts on purpose. If one looks at his character overall (which is what is supposed to be, considering every character has many different parts that make them up), everything he does makes sense, and every bad action he commited had a reason. If he didn't commit those bad actions, it's confirmed that worse things would have happened. He was just thrown into a bad situation every time, starting from the time he was 4 years of age. Hence why people like Naruto wish to change the shinobi system. It's failed alot of people in the past and quite a few have had to give up their lives for it. Itachi being the most extreme example of that, then others like Kushina, Minato, Jiraiya, Neji, and a few more.