Jeez, can I pick my current favourites?
I don't think I can nail down a list of all-time favourites, but I'll give it a shot:
Metallica - Nothing Else Matters
It just fits the song so well and works as a tension release from the rest of the song
Metallica - Bleeding Me
When Kirk kicks back in to mimic the chorus melody, the wah sound is just plain awesome and it sounds so amazing.
Metallica - Unforgiven
Just freaking cool and perfect in the song.
The Tea Party - Cathartik
The solo fits the mood of the song perfectly, and is a little flashy at the same time. A cool song overall, it's in 3 tunings (one for verse, one for chorus, one for solo...and they pull it off live
)
The Tea Party - Temptation (live version)
It's not complicated, but it just sounds really cool with the effects he has on there, and totally different from anything they'd done before.
I Mother Earth - Soft Bomb Salad
Very flowing and melodic, it's almost hard to tell where it ends, because it just flows back into the next guitar part, very fluid.
I Mother Earth - (pretty much anything off their last two albums)
What can I say, most of my lead guitar playing style comes from this guy. He's just awesome.
Coheed and Cambria - Welcome Home
The two guitarists trade solos back and forth, each with their own style and sound, and all of it is so melodic, you can sing along with it (and it'll even get stuck in your head)
Coheed and Cambria - Final Cut
Pink Floyd tribute all the way (no, it's not a cover). First solo's very fluid and drenched in a nice phasing/flanging? sound, second solo's very clean and Gilmour-y.
There's lots more, this is just for now lol There's some nice ones on the new Disturbed album, and on everything Opeth and Porcupine Tree have done.