Sasuke's characterization is a stuff of Greek Tragedies. His descent to madness reminds me of Macbeth's final moments. When he killed Danzo and Itachi, those moments were the pinnacle of writing and imagery from Kishimoto. The manga attained those heights and never achieved those moments of verisimilitude again - that look of void as if Sasuke had been inside the maw of darkness and back again. Wonderful.
There isn't a character that reaches Sasuke's level of realism and humanity. I can challenge anyone to prove me wrong with an actual literary debate, as my knowledge on Literature is pretty solid. I do not care about opinions in this regard, henceforth truth be told, you may not like Sasuke ... that is your opinion, but when you state that he isn't a well-written character, your opinion is backed by your poor judgement of writing and is a supremely poor opinion by extension. So, no one should commend you for it. You should actually be called out on it.
Danzo, Kabuto, Gaara, Guren (filler), Kimmimaro are way better.
I get that these are opinions, but dear lord, you must be joking for the bold ones, if you are counting Part two Gaara's development. He is the most poor character in the manga, if one considers the second part as well. Kimimaru is half-decent, so I wouldn't throw him down the poor characters list.