My favourite hide solo is the one he plays in Rusty Nail. It's not as shreddy as many of his (earlier) solos, nor perhaps as heartfelt as the solos he plays in the ballads, but it's so damn cool =) It's absolutely perfect for the song and it's place in the song, and it adds so much.
Other favourites:
Jani Liimatainen (Sonata Arctica) - Black Sheep
Many of Jani's solos are just mindless shredding, this one is a little different. It consists of a few different sections and, imo, is really well constructed. Speed picking -> tapping -> cool slidey part -> speed picking. I love it.
Kristian Niemann (Therion) - Everything
I think Kristian Niemann is the best guitarist ever. His solos are always "tasteful", exactly what the song they are in needs. He has amazing technical skill, but doesn't treat every solo spot as an opportunity to show off how fast he can play.
Luca Turilli (Rhapsody) - Gargoyles, Angels of Darkness
He plays a couple of solos in this song, and they blow my mind
"The dream is alive, with the moon on the hills every night,
Run around and see another side of the dream
Freedom has a meaning for me, you can't tame me!!!"
