I just don't think I can choose! Wen he was first sired, and for a fair few years after as well, he was definitely obsessed with Dru. Also when they 1st came into the show he was pretty obsessed with her.
But he was also obsessed with Buffy from the 1st time he saw her. He either wanted to kill her or just wanted her, culminating in 'that secen' in S6 that many people just can't watch:(

Obviously Buffy! He was totally obsessed with her from the moment he laid eyes on her - first obsessed with killing her and then loving. He was obsessed with Drusilla, but mostly because she was his sire and he loved her. He wasn't totally crazily obsessed though, and em_em is right in emphasising that scene in season 6 "Seeing Red".

Both. But I think that he was always obsessed with hating or loving Buffy whereas with Dru it wasn't as strong.

i find spike was really obsessed with buffy because he was stalking her and made a robot with her image. i think that angel was more obsessed with dru, it was angel who stalked dru, not spike.

Buffy. I think he was genuinely in love with Dru

Spuffy

he was definately obsessed with buffy it was kinda creepy when he had warren make the buffybot.

Spuffy forever.

No doubt. His relationship with Buffy was far more interesting.

Both, but he stalked buffy and made a robot her lol but he seemed have twisted obsessive love for dru as well but with buffy it seemed more intense

Both. He seemed to get obsessed with anyone he fell for.