Soul Force (and Zeta Wing) are good C64 shoot-em ups, with a lot of design effort into making them enjoyable as well as making good use of the C64 technically.
Sure, it's using the C64 character mode with animated characters to simulate parallax and other moving objects, but that works very well, and the CPC cannot do this at 50fps, obviously because that's a strength of the C64 (with its own limitations). The Plus can get closer, the hardware scrolling and sprites can free up CPU time to do spot animations in the background.
Alcon looks excellent as well, and it's hard to do these games on the CPC and retain smoothness, so it's great to see it.
Really, it's win-win all around.