IMO RoB is the hardest game to get to work on a PCE emulator because you need the disc or an image and CD tracks. Any other PCE game would not be worth having a standalone exe. By the way, I really like it. Especially the scanlines!
I have one for Rondo (have it two other ways in real life), Zero Wing PCE CD, Super Darius 2, and Gradius 2 (got the real thing of this one too). There's plenty of good stuff on the PCE CD that is worth doing this for, including Forgotten Worlds and Super Raiden. Also PCE emulation is not that hard, ISO's are quite easy to find, you just have to know where to look.
Edit: Someone mentioned the 4 Valis games, yes, so good that I downloaded and burned these bad boys to CD long ago.