Mind if I play? This is my single favorite subject, so...
Obviously I excluded Theocracy (heh heh), but here are the best of all time for my money. I tried to put these in some kind of order, and I could only narrow it down to twenty (and that took a LOT of work). So without further ado...
20) Kamelot--Center of the Universe
Always loved Khan's smooth, unique voice. I eventually lost interest in Kamelot, but The Fourth Legacy and Karma were great albums. However, I think this is their single best chorus (1:22-1:46):
19) Twilightning--Plague-House Puppet Show
Kind of an under-the-radar band for some, but what a voice and what a chorus (2:00-2:18)!
18) Rhapsody--The Wisdom of the Kings
They don't come any cheesier than Rhapsody, but they sure could write an epic chorus back in the day (1:47-2:09).
17) Masterplan--Enlighten Me
Just a fantastic chorus, set up by one of the most effective keychanges of all time (0:51-1:20).
16) Gamma Ray--Rebellion in Dreamland
No Power Metal list of any kind can leave this song off. One of the cornerstones of an entire genre. Bonus points for the hilarious video! (2:01-2:29)
15) Edguy--Tears of a Mandrake
In my opinion, Tobias Sammet has surpassed everyone to become the greatest Metal songwriter of all time, so you'll see more Edguy and Avantasia than anyone else on this list. I'm a little burned out on this song now, but it (and the whole album) was a huge influence on my writing (and the big choirs), so I couldn't leave it off completely (1:57-2:29).
14) Serenity--Coldness Kills
Maybe not strictly Power Metal, as they have some prog leanings as well, but this is one of the best choruses you'll ever hear in any genre. Another of the most effective keychanges of all time. (1:44-2:05)
13) Blind Guardian--Mirror Mirror
The kings. Respect. (0:43-1:06)
12) Sonata Arctica--Full Moon
Tony Kakko is my second-favorite Power Metal songwriter ever, so you'll see a lot more Sonata on this list as well. This is a bona-fide Power Metal classic, and "Run away! Run away! Run away!" is one of the best singalong moments at any live show (1:59-2:22).
[ame]http://www.youtube.com/watch?v=-DBodkYOe2M&feature=related[/ame]
11) Rhapsody-- Emerald Sword
The first Rhapsody song I heard, and while I lost interest long ago, this remains their greatest moment in my opinion (1:50-2:11).
10) Sonata Arctica--San Sebastian
Just textbook speedy catchiness (0:56-1:18).
[ame]http://www.youtube.com/watch?v=r4y-MSEOy3s&feature=related[/ame]
9) Avantasia--The Scarecrow
There's just a magic in Tobi's melodies that no one else quite seems to capture. I'm not sure exactly what it is, but I use an extremely scientific measuring technique called "goosebump factor." (1:55-2:17)
8) Nightwish--The Poet and the Pendulum
It doesn't get any more epic than this (2:32-2:59). Tuomas is my third favorite Power Metal songwriter of all time.
7) Sonata Arctica--Aint Your Fairytale
Of all Tony's "wolf" songs, "The Cage" gets way more attention...but this is the better chorus (1:09-1:34).
[ame]http://www.youtube.com/watch?v=sw4Odd6nues&feature=fvsr[/ame]
6) Sonata Arctica--Dont Say A Word
The ultimate drop to half-time, "everybody jump up and down in unison" chorus (0:50-1:08).
[ame]http://www.youtube.com/watch?v=dP4x-Df5Iqo&feature=fvwrel[/ame]
5) Edguy--The Pharaoh
Epic. Massive. Choirs. (1:39-2:19)
4) Avantasia--The Wicked Symphony
Russell Allen's (Symphony X) voice singing Tobi's melodies? Um...yes. (2:59-3:32)
3) Nightwish--Dead to the World
This list was extremely difficult to put together, but the top three were not. It would take something pretty gargantuan to ever change my top three. This whole song is a masterclass in arrangement, and especially in the effective use of keychanges.
(1:55-2:22)
2) Avantasia--Sign of the Cross
The second-best Power Metal chorus of all time (1:31-2:00).
1) Avantasia--The Seven Angels
No surprise here; greatest Power Metal song of all time. But seriously, what else could be #1? (2:48-3:23)