People like Itachi because of his backstory and how well-written he is. He's has alot of depth. They like his sacrifice and they notice his mental-strength. He never gave in to hatred even though his life sucked the most. He's also one of the few shinobi in the series that is the closest to being an actual ninja when we think of one (not bashing Naruto, but shinobis do not wear bright orange jumpsuits!). He's very smart and has alot of power, but he's also one of the most humble characters in the series. He also has a very cool character design. People also like his love for his little brother, and they like the fact that he cared about his village and clan. They also like the fact that he's very talented and worked hard from an early age. He acknowledged his mistakes, even though he had no better options. He just has many admirable qualities that make it hard not to like him. He isn't perfect though.
Minato has a nice attitude and is fast. But he is far from perfect.
