Both the Genesis and the CD are new. Well, new in the sense that I only recently purchased them. They're old as dinosaur shit.
God this thing is a behemoth.
I couldn't get it to even boot up for a while, so I had to take it apart. The cord connecting the CD drive to the CPU came loose, so I had to plug that back in.
Came to a point where the bootup screen came up, but the CD tray would keep spitting the games out. Took it apart again. A switch was out of place, which was preventing the CD tray from properly closing. Put the switch back in place, reassembled the system. Tried it again. Strange grinding noise coming from the console. Turns out, I forgot to put one of the pieces back in place that protected the game from being scratched. That's pretty important. Took it apart again, put the piece back.
Success!
The Genesis works too.