There's TONS of favorites for me, but these 3 come to mind instantly as solos I could listen to forever:

1) Bad Attitude- Chet Thompson- Hellion. He had this throw down groove in his playing that really shines on this song. Without a doubt my favorite guitarist from the 80's Head Banger's Ball bands.

2) The Legacy- Alex Skolnick- Testament. Alex is just awesome and even though the song is a ballad I love it. Shame he doesn't do stuff like this anymore.

3) Comfortably Numb- You know who- Pink Floyd. Self explanatory.

Also the "We're Stars" compilation solos never get old to me.