It took me a while to figure this out. I thought I was bamboozled! I finally put together a Sega Master System from a box lot, an eBay auction, and a Bull Moose transfer from NH. 3 out of the 4 games were this motorcycle game paired with a shooting game. While they were cool and all, I wanted to try what else the Master System has to offer. I tore open the cartridges, and they were all different cards. Nope, not counterfeit copies or swapped cards.
It turns out that the Master System is so cool, it came with Sega’s idea of Mario Bros / Duck Hunt – on the system! When it can’t read the cartridges, it loads the internal game. I cleaned the cartridges that didn’t load, and they worked fine.
I hadn’t ever seen a Master System in action. Mine was a Nintendo house, and by the time I met my best friend Stephen, he had moved onto the Genesis. I have to say that I’m quite impressed with their 8-bit system. Excellent graphics and sound, 8-way d-pads on their controllers, and what appears to be the option of playing cartridge or card based games.