...so how about a discussion? Who knows anything about the mysterious, unreleased Space Fantasy Zone? From the reviews I've tracked down and read (thanks to Google), it was an NEC-made hybrid of Fantasy Zone and Space Harrier for the PC-Engine. Apparently, the release was cancelled due to legal issues between ol' Sega and NEC, so the project ended up being canned.
Sometime near there, however, some kind of preview (or perhaps a leaked full game) was put onto the cover CD of a Japanese magazine. From there, it got onto the internet, and the rest is history. All I can find now is the main theme from SMS Power. A mix of Space Harrier's main theme and 'Opa! Opa!' Nifty stuff indeed.
So, as they say: Discuss.