Here's some more
Phantom of the Opera (musical)
Nightwish (They have had two different singers with two different stiles, one singing opera and one not. I like them both. You can try "Over the hills and far away" and "nemo" for Tarja (first singer) and the new album "Imaginaerum" for Anette. I will also highly recomend the song "While your lips are still red" which is sung my the bassist, Marco, and a lot calmer than the rest of them.)
Lene Marlin (She's Norwegian, but sings in English)
Ali Project (They sing in Japanese, and I find their melody very special, I have no idea what to classify tham as..)
Hans Zimmer (He writes soundtracks, and have made music for ex. Lion King, Pirates of the Caribbean, Inception, the DaVinci-code, Spirit-the stallion from Cimarron and a lot more. He only makes the melodies, as other artist are singing.)
Kamelot One of my favourite bands. I would recommend the album "The Black Halo", it's really good. Their early songs had another singer, but I like their music best with the singer Roy Khan)