Why would anyone "hate" Dante? He's one of the coolest protagonists in a video game EVER. xD
I don't "hate" him, but I certainly dislike him. He's not cool, he's campy. He's got ham and cheese to pass around and then some. He's a boring hero because he's damn near invincible. There's no suspense, you always know "Dante's here, everyone evil dies." There's almost no point in playing the game because he's just a twot.
Now in DMC1 and 2, he didn't seem so full of camp. He had weaknesses and vices, he showed emotion. Hell, at the end of 3 he began acting much more like his DMC1 persona. But 4 pulled the rug out from under continuity and told it to go blow itself, because though 4 happens after 1, Dante is nowhere near as mature as he should've been. He acts like a complete ass clown and doesn't take anything seriously. Why? Because he's a boring invincible hero. Nothing is a threat to him and he doesn't even break a sweat.
TL;DR Dante became one-dimensional in DMC4 and Nero had a more flexible, rebellious personality, making him more likeable in my opinion.