What are the songs that end the best, in your opinion? The ones where you say "that's perfect"!
For me, I tend to dislike fadeouts, except where it's cool and fits. The guitar at the end of Rush's "Take A Friend" off the first record is an example of this exception. That fadeout is cool.
I particularly dislike the fadeout where there's a repeated chorus or a lead going on. Again Rush with the end of "Different Strings". Drives me bananas (insert monkey sound of your choice).
I have three that stick out:
1) Starless (King Crimson) - after the hypnotic Fripp guitar, the Neil-Young like one note lead

and the rabid Mel Collins lead where the Wetton and Bruford just go to town, the last 30-60 seconds with the mellotron and the Wetton thundering bass line are just earth-shattering!
2) Natural Science (Rush) - after the third section...right after the Gedster sings "Sensitive, Open, Strong" there's that dum dum dum da da da dum...then they go into the famous "Rush jam"....ending in the last few power notes and the waves...it makes we want to run through a wall! Xanadu's close, that's a great one too.
3) Miracles Out of Nowhere (Kansas) - just an incredibly constructed song. Right after everyone sings "Out of Nowhere".....the band comes in for a jam, then stops abruptly, with the organ playing down the scale, finally ending with the gong crashhhhhhhh. Good to see a gong used elsewhere besides a heavy-metal drummer's kit.