Spike...absolutely no way. He was the ultimate Big Bad, through and through. Like Kean said in the other thread, he changed because of Buffy, the influence of the people around him. He was chipped because he was caught after going back to try to kill her one more time, so without Buffy, there would have been no reason for him to be in Sunnydale at that point. The Night of St. Vigeous, or however it's pronounce, would have went off without a hitch, because, without a Slayer to tempt him, Spike would have waited until the actual night, and that would have been that.
So, no, without Buffy, Spike would have continued the life he'd had in 'School Hard'. Maybe he would have stuck around the Hellmouth, maybe not, but there would be no way he'd be anywhere close to being a Champion.
Angel, on the other hand, is different. He was helping people before he met Buffy. Alright, it didn't go very well any of the times we saw (except when he rescued the puppy, lol) but at least that instinct was there. He has his soul, so he knew right from wrong, and he knew when he needed to help people. I doubt he would have ended up as the Angel we all know and...tolerate, for some people, lol, but he wouldn't have been evil.