I've been checking out Kiske's solo work, and sadly, none of it comes close to what he did with Helloween.
The self-titled albums aren't very good, Supared is good pop rock, but not metal, Same goes for the new "Place Vendome" album - some of the best AOR I've heard in a while but definitely not metal.
I'd go with any of the other "spin-offs"/solo projects anyday; Masterplan, Gamma Ray, Primal Fear etc.
There's no denying that Kiske's one of the best vocalists out there (he's on my top 10 for sure), and that makes it even more a shame that we only get to fully enjoy him when he makes guest appearances (Edguy, Avantasia, Masterplan and others).
The new Keeper album is high above anything Helloween have released in the past 10-15 years, but I still prefer the original two. I can't make up my mind as to wether this is truly deserving of the "Keeper" name. It has some amazing tracks, some really great, and a few not-so-good ones. I guess it's Deris' vocals that keep putting me off. I just can't stand him after a few listens, and I feel like going back to the Kiske era. But that's just me.