Have loved Savatage for years, and I concur that wintertime seems to be the best time to listen to them! I love pretty much everything from Hall of the Mountain King on, the early albums are good but not as special as the later ones in my opinion. I love both vocalists, I prefer Zakk's voice as a whole but Jon gets so much emotion into his, you can really tell he was giving it his all. They've also had a string of amazing guitarists, Criss being probably my favourite but the ones that followed on are absolutle beasts in their own right.
I probably would say Edge of Thorns is my favourite album, the combination of Zakks vocals and Criss' guitar playing just edges (haha) it above the rest, that being said I really love every album and listen to them a lot. TSO are great fun, I listen to them a lot around Xmas and they are immense live also!