You know, I think I like every Spike pairing (minus Harmony). I voted for Spike and Angel not because I really want them together in a romantic way, but because I just love to watch them annoy each other. They're so funny!
I really liked both Spike and Dru and Spike and Buffy, though.
He's just a good boyfriend. JM had it wrong when he said Spike wasn't. I mean, yeah, he's obsessive and freaky, but he was really tender and forgiving with Drusilla. And with Buffy. They both abused the crap out of him, and he only flipped his lid over it like one time each. He's the kind of guy who'll marry you if you give him half a chance. He'll stay with you through the ups and downs -- and we're talking serious ups and downs when it comes to the Buffyverse. He'll withstand torture to keep you safe. He'll love the entire package, warts and all instead of just the good parts. He'll be able to handle and even appreciate your dark side. He won't need you to be some paragon. He'll even challenge you to meet your potential -- and to deal with his warty, non-good parts, which are considerable. I mean, man... he's just a good boyfriend, in his own particularly frightening, vampy sort of way. If I weren't married already and Spike came knocking on my door, I'd seriously consider him -- fangs and all. Just the way he used to look at Dru and eventually came to look at Buffy... all that wonderment and passion and love... makes a girl melt.
So I guess I'd go for any pairing, provided he really loved the chick. That's what makes Spike special: his capacity for love. Spike pretty much rocks any relationship. He's a lot better in that department than, say, the Parkers of this world.