Well, you gotta love the German trio which started it all, really:
Blind Guardian, Gamma Ray and Helloween
Personally, like many others I think Blind Guardian has gone the furthest with the genre, becoming very progressive and extending the genre of power metal even further. They are the 'Death' of PM
Also, I recently found 3 Inches of Blood, and I'm in love. 'Advance and Vanquish' is an amazing old-school/new-school mash-up of speed/power metal and with a slight metalcore edge to the music. It's fist-pumping, energetic and tons of fun, and I can't rec them more
Other great bands would be Rhapsody ("of Fire") and Symphony X, the latter of which has the amazingly epic track 'The Odyssey' which is a 25 minute - re-telling of the greek epic of the same name.
Aaaaand that's all for tonight folks. Later
cheers,
--N