I could never give an answer to that question that I would be happy with if that makes sense :-)

My favorite at the moment though is the solo in Priceless by incubus. Just unexpected, technically quite nice and converse to Mike's usual playing style and I can always remember the first time I heard it and how baked I was! It was and still is out of this world imo.

This question is more loaded than the 'best guitarist' question. That said, 'Sweet Child' is also one of my favorites. It was one of the first solos I tried to learn but it took me years before I could play it even halfway decent. The quality at which I have been able to play that solo has helped me track my guitar progress over the years.

Always handy to have a benchmark to measure progress and improvement.

I like insane speed, wicked technique, and general face-meltiness. That being said, my favorite solo of all time is the first one in "Comfortably Numb" by Pink Floyd. It's everything a guitar solo should be, IMO.

there are so many great ones, i could not possibly pick one as the "best", and my favorite changes about once a week.

freebird
stairway to heaven
sweet child o mine
la grange
sweet home alabama
im bad im nationwide
voodoo chile
statesborough blues
enter sandman
honky tonk women

the list goes on and on and on ............

and for me the "best" solo/lead work doesnt always have to be super fast or highly technical. somtimes something simple can sound perfect. john fogerty, among others, comes to mind when i think of stuff like that.

Blackbird by Alter bridge.
It's not my only favorite but it's the one that comes to mind right now.

Like Johnny said there are too many great solos to pick just one
Iam not saying these are the best guitar solos ever or anything but some of my favorites
EVH-eruption
Steve Vai-Tender Surrender (is it a solo or a song lol)
Metallica- The Unforgiven and One
Pantera-Walk
Pink Floyd- Another Brick in the Wall(simple but awesome)
Jimi Hendrix- Pick one!
Stevie Ray Vaughn & Carlos Santana - Traffic Jam (its all insurtmental buts its awesome)
BB King-Three O Clock Blues
Zakk Wylde-Farewall Ballad(R I P dime)
Alice in Chains- Man in the Box
Bucket head-he does crazy stuff like the theme to halloween and Jordan is insane

Oh yeah check this out too its just sic http://www.youtube.com/watch?v=2iLIhLv8LuY

I like Avenged Sevenfold, the stuff doesn't sound that complicated but it can get really technical. For example the main theme to "The wicked end" which goes:

(quick version)

e:--13--10---------------------/17--16--|
B:------------10--9------------------------|
G:---------------------10--9---------------|
D:-------------------------------------------|
A:-------------------------------------------|
E:-------------------------------------------|

Which isn't too hard except for the speed.

That isn't a solo, just an example of the guitar, there are solo's and all around kick a** playing in most all of their songs, some of which are:
"Afterlife", "Crossroads" and "Lost" all of which can be found on their new CD named Avenged Sevenfold.
The names of their guitarists are Zacky Vengeance and Synyster Gates.

The second example is Megadeth. They are one of the most recognizable bands to anyone who has dabbled in metal. guitar wise the can usually be compared to metallica, and singing wise.. i dunno.

As you'all say -- there are many great solos, very genre dependent. Two that particularly come to mind right-now are based on pop-music.

Joe Walsh does a very melodic, well phrased solo on 'One Of These Nights' that just FLOWS. Very nice.

And what was that Eddie Van Halen solo on one of Michael (yes, I am black!) Jackson's tunes? I remember that totally making the tune. Anybody remember ?