Here is a reminder that the Sega CD had more than Sonic CD:
Ecco The Dolphin:
While not as good as the Windows 95 version, this game is much easier to play unless you have a Windows 95 or Windows 98 computer that still works. Do remember hard drives don't last that long even if everything else in the computer work and trying to make these Sega ports to Windows 95 work on modern computer is quite hard.
Earth Worm Jim, Special Edition:
The second best ever version of the first game, and without the headaches of making the Windows 95 version work on modern PCs. It even has an extra level compared to the Sega Genesis version, so that's two levels more than the Super Nintendo version!
5 in 1 Sega Arcade Classics:
This is the game that came with your Sega CD if you were lucky. Four of the five games are better than the Sega Genesis versions and is definitely a game you should have if you have a Sega CD.
The Lunar saga:
Both Lunar Silver Star Story and Lunar Eternal Blue have become cult classics for a reason, they are two games in two CDs and in different boxes but I put them together because they are from the same series.
Popful Mail
Now this is sadly a mostly ignored game despite the Sega CD having the best version. Think Lina Inverse from Slayers if she was an elf, and with less destructive power.
Of course if you want to know more, there is Google.