Gamma Ray. Simply one of my all time favourite bands. The run of albums of Land of the Free, Somewhere Out In Space, Powerplant and No World Order is power metal simply at its best. I love the three Ralf albums also, they are great hidden gems, Insanity and Genius could be included in that run of albums.
Majestic and Land of The Free 2 were amazing also, with LOTF2 being a top 3 Ray album for me. The last one To The Metal, was decent but lacked what LOTF2 had. What I also like about Gamma Ray is that they have had a consistent lineup since 1997, which shines in their music.
I love Helloween also, and I'm one of the ones that prefers the Deris era over the Kiske era. Master and Oath are both excellent, but if you want Helloween at its best, you must check out, Dark Ride, Better Than Raw, Rabbit Don't Come Easy, Keepers 3, Gambling with the Devil and 7 Sinners. If anything, Helloween have become much more reliable and consistent than Gamma Ray over the last 5 or so years.