The Sega CD version of Mortal Kombat wasn't part of the initial "Mortal Monday". They took a little extra time to add a grainy music video, high-quality music, and slightly updated graphics.
Play control:
Basically the same as the Genesis edition.
Graphics:
A slight upgrade over the cartridge, but not enough to bump-up the ranking.
Sound:
The background music is great, identical to the arcade.
Other Factors:
See the loading screen to the left, get used to it. If that's not bad enough the game totally freezes to load music whenever you execute a fatality. Oh it gets worse.. whenever Shang Tsung transforms you get a nice ~5-10 second delay.