I've always thought Deep Purple's Sweet Child in time was a difficult vocal, seeing as Ian himself can't really do it anymore. I was looking at some Youtube covers and found a few with the vocal chops,
Germany's Roxxbusters does a decent job on the vocals (only)
https://www.youtube.com/watch?v=MtHrjUMyKmM
although poorly recorded

and Belarus's Petr Elfimov hits all the notes in this (over orchestrated) version.
https://www.youtube.com/watch?v=dnU25je3Ebw

but this kid bangs out the best rendition of just the first part IMHO,

a semitone higher than Ian, and he's mainly a guitarist, covers Yngwie tunes etc.