This is some sort of trick. Some sort of clever trap I am ill prepared for! :P
Nevertheless, I have a few things to add:
1: I do actually think Surtur wins this fight. See my first post.
2: Surtur is typically shown much larger then that one Hulk clip, yes, although it's hard to judge with certainty because his scale is sort of all over the place from scene to scene. I think he's bigger then Ghidorah for sure.
3: Even if you give Rodan a pass on temperatures, the volcano was mostly a sheer force / shockwave / kinetic energy explosion thing. The lava wouldn't have bothered either of the alphas either.
4: I have sooooo much to say about the nuke stuff but I'll let Tomzilla have a pass at that first seeing as he brought it up. I dont think the Superman analogy quite works though.
5: You are asking specifically where I would put their damage output in terms of scaled events like city busting and whatever? Hmm. I'll have to think. Sharp seems to think (in a recent thread) that a character named Grougaloragran would have trouble hurting the top tier Titans, and Grou can reshape shorelines and get punted through mountains in his fights. Not to throw Sharp under the bus or anything here with the name drop- I've just never bothered to think of the damage scale in this way so I'm not sure how to respond.