It would be impossible to name one band or song as having "The Best Solo", but I love the lead guitar on these songs:
Tech metal/ emo/ metalcore:
I Am Abomination - "Since 1776" Good Fight Music - YouTube
Rock and roll/ southern rock
Clutch - "Electric Worry" DRT Entertainment - YouTube
Spanish-influenced acoustic
Breed 77 - Breaking The Silence (Acoustic) - YouTube