Child In Time from Deep Purple's In Rock contains my personal favourite solo. I was a young stressed out adolescent when i first heard it. My brother in law had all these old records and it simply blew me away.
It is chaotic and obviously improvised and at times sloppy. But hey I will treasure that moment forever.
Petrucci- Under a dark glass moon or whatever its called is brilliant.
Holdsworth- Devil take the Hindmost-Just listen and be amazed.
Armored Saint- Warzone, check out LA metal at its best. two great guitarists at the edge of their abilities.