Sapphire for sure, just for the visual experience. Blazing Lazers... my second Turbo game ever (1989), and just an awesome introduction to not only shooters, but to the TG16 as well (Keith Courage doesnt really count). Gate and Lords of Thunder... badass graphics/music/gameplay, really shows off the SCD potential.
While I have yet to experience the Soldier series, I definitely want to play these soon. Probably be the PCE versions as the US ones are kind of costly. They seem to resemble Blazing Lazers alot, so I'm sure I'll love them