I find The Marriage of Heaven and Hell Part II the best Virgin Steele album, but Part I and Invictus (all of the same trilogy) are very strong as well.
I recommend all three. Also very cool, although sometimes a bit "over the top epic" is Noble Savage. That title track is brilliant, but I am not sure if you'll stand the vocals in the last couple of minutes. There are more strong Virgin Steele songs I'd love to recommend (there are also some nice compilation albums), but if you go for whole albums, then these four are the ones, imo.