Oh good one. Also I remembered Wachenröder but it seems someone else caught it before me.Astal (Sega Saturn). Awesome plataformer, great music and art style.
I do too, but it's obviously part of a franchise... -_-Panzer Dragoon Saga
And I want a remake soooooo bad
OP, you have Illusion of Gaia and Terrenigma listed, but both of those are part of the same series, which started with Soul Blazer.
Enemy Zero is the sequel to D.
Super Airwolf (Mega Drive / Genesis) was a pretty rad game. solid shoot them up and top down shooter mechanics. Difficult but not overly so.
Transport Tycoon had the Deluxe version which I enjoyed hugely but man that's probably my number 1 game I'd like to see a proper sequel for. I don't really count the iOS/android versions. I still need to get around to playing Chris Sawyer's Locomotion.
Theme Park deserves a sequel too. Theme Hospital does not count as a sequel to Theme Park!