These questions always make me laugh, regardless of what character they're asked about.
I think he'd be exactly the same as any other person. It all depends on the situation, the occasion, the partner in the relationship with him, the nature of the relationship, and how they're both feeling at the moment. Are they friends & lovers, or are they just together for the cold, empty, prefunctory screw?
I have no idea what he'd be like. But I guess that's what makes him the perfect lover, really. He is whatever we each imagine him to be.
"Would". Is the wrong word. But I'll answer anyway.
In my mind
I think he would be a relativley thoughtful and careful lover. He would aim to please his woman in whatever way he could(during both the naughty and every day life)He would do his best to make heras happy as possible. But like every other man, Severus cant always give his lover their way, and he'll want what he wants. Then i think he would be a more dominant, possessive being, but not cruel, just demanding.
But In a romantic sense, I see him as sort of a dark,romantic lover, like the single red rose, you are my life, Die for you kind. Maybe a little insecure of himself and unsure of his lover at first, but once he gains footing, he is a good, solid, stable lover.
Plus I dont see him as a "we just wont work" kind of guy. I dont think he really loves often, so when he does, he wont let go that easy. So he might be possessive as well. And protective.
He views himself as screwing up with Lily, so he wont make that mistake again, and he will protect his woman.
Sort of secluded though. He wants his space, and wont be all up in her face and her buisness, unless he needs to be. but like I said before. Demanding.
Only my fantasies though. Oh if only if only
Oh and as Lady Nottingham said ^^ above, if he was a dominant being, he wouldnt be cruel. he would be faithful and protective, and truly in love with whoever his submissive was.
Well, I can't say what kind of lover he would be, I can only say what kind of lover I'd want him to be. I'd want him to be a little shy at first, tentative, and then as he grew to trust me, passionate, fiery, and a little dominating and possessive.
I think he'd be very dominant and demanding, and a bit, or a lot, on the rough side, depending on what you wanted from him as a lover. I think he'd be very interested in excelling at pleasuring his woman, just like he's a perfectionist in other areas, like brewing potions. While he's a rather conservative man in public, I think he'd be a lot less conservative in the bedchamber, and would be willing to roleplay, and try out new things. I think that, because he's so buttoned up on the outside, he'd be quite easily incited as a lover in private, and almost perpetually horny at the slightest encouragement. Sex would be like a competitive sport with him, I think. But competitive in a very good way! And he'd appreciate a little humor with his sex as well. My vision of him is a man who very much likes sex, who would want a woman who does too.