Fight takes place in San Francisco. Morals off. Death for the win. Classic Versions. No Prep.
@Gritterr: Well during Secret Wars, The Human Torch went Nova and managed to fry something inside of Ultron, and that took him out. I'm not to well versed on Ultron though, so that may have been a bit PIS-y. I mean if it's so easy to just destroy something important in his insides, then why don't The Avengers just do that every time they fight him?
Without prep I believe the team loses. Wolverine can't cut him and storm's lightning can only do so much but I can see the bolts at least slowing him down. Adamantium is still a metal and a good conductor of electricity. Unfortunately classic Colossus gets taken down after a little run. Modern Colossus(no jugs) fully trying, would give Ultron pause and maybe even hurt him but Colossus's support isn't enough.