I'm glad you liked the Revelation album. Since you liked that, I would of course also recommend the band's other works, especially
Release, their prior album, as the new one is an extension of that. Many of Against Nature's works would be highly relevant as well, as that band is merely Revelation under a different guise and more open to experimentation.
Appease,
Panoply,
Safe Dissonance,
Leer,
Ghosting, and
The Anxiety of Influence are the most similar to Revelation, and not coincidentally, as these are the albums recorded before the original line-up of Revelation reunited. Once Revelation was back in place, the floodgates of experimentation really opened up.
Action at a Distance is totally keyboard driven with no vocals and no rhythm guitar, for example. It's still excellent though, so you may still be interested. Of course everything either band has done is available for free download.
As Revelation is heavily entrenched in the Maryland Doom scene, these other bands could very well be relevant to your interests: Asylum/Unorthodox, Internal Void, Iron Man, The Obsessed, and other bands who were associated with the scene, like Blood Farmers and Penance/Dream Death. Obviously Pentagram too, the god father of them all. Excellent newer doom and doom related bands include Valkyrie, Ogre (now defunct), The Gates of Slumber (though I prefer the earlier material), Apostle of Solitude, Orodruin, Argus, Pale Divine, Memory Driven(/Dwell Within/Oversoul, band led by the leader of the ...
Yet So Far era Revelation), Lord Vicar (ex-Reverend Bizarre), Procession, Reino Ermitano, Fall of the Idols, Griftegard, Jex Thoth, etc., etc.
As for older US power metal stuff, most of it was not as technically and musically accomplished as Riot. That scene was typified more by young, brash enthusiasm and balls-kicking riffage, so to speak, though that's of course a major oversimplification of things. Some of my favorites from that era include Cirith Ungol -
King of the Dead, Manilla Road -
Crystal Logic, Attacker -
Battle at Helm's Deep, Helstar -
Distant Thunder and
Nosferatu, Liege Lord -
Burn to My Touch and
Master Control, Omen -
Battle Cry, Griffin -
Flight of the Griffin, Savage Grace -
Master of Disguise, and Fates Warning -
Awaken the Guardian. I suppose that's enough for now. Relevant links:
Revelation
Against Nature
Asylum (cuts off for some reason, can't find much else)
Unorthodox 2
Internal Void
Iron Man 2
The Obsessed
Blood Farmers
Dream Death
Penance
Pentagram
Valkyrie
Ogre
The Gates of Slumber
Apostle of Solitude
Orodruin
Argus
Pale Divine
Memory Driven
Dwell Within
Lord Vicar
Procession
Reino Ermitano
Fall of the Idols
Griftegard
Jex Thoth
Cirith Ungol 2
Manilla Road 2
Attacker (The Hermit in particular)
Helstar (Baptized in Blood in particular)
Liege Lord
Omen (Battle Cry in particular)
Griffin
Savage Grace
Fates Warning 2
I've also written reviews for many of the newer albums that I mentioned (Revelation, Against Nature, Unorthodox, Valkyrie, Ogre, Apostle of Solitude, Reino Ermitano, Fall of the Idols) that you can read in the third link in my signature.