I have used Richard Bannister's emulators since 2005. They haven't failed me so far. I'll give this one a go too.
Apparently you haven't since "For the first time, the ‘It just works’ philosophy now extends to open source video game emulation on the Mac".
Versus the typical emulator author, this team seems to have exchanged hostility towards users for egomania.
I know ROMs have been around for a while... But how do people get the data from the cartridges on to a computer? Are cartridges simply "old-style" thumb drives with different shapes? I feel so elementary asking this question this way but I'm not familiar with the tech and I don't know how to word what I'm saying.
Video game cartridges vary a little.
Most games on most consoles are just read-only memory chips. So there'll be some pins that act to communicate a memory address to them and some pins that act to return a value back to the device. If you were to cycle through every address and assemble every value you'd get an image of the game.
Most consoles explicitly allow the cartridge to be a bit more complicated by extending a few more signals onto the connector. In the Mega Drive there's a signal you can send to switch it into Master System mode. On the Game Gear you can take direct control of the LCD. But such cartridges tend to be the exception rather than the rule.
Some cartridges for simpler systems, like certain titles for the Atari 2600, incorporate a little memory management unit that can remap different parts of the source ROM into different parts of the visible memory space depending on which value you write to a certain location.
Some systems, like the NES, are more or less built around the assumption that cartridges will be smart, with the various types of memory management unit, additional sound chip, etc, bundled together as a purchasable configuration.
Then there's stuff like Virtua Racing and Star Fox that is almost a complete separate console that happens to communicate with the original via the cartridge slot — the base console doesn't enforce that the value at a particular location will always be the same so a cartridge is technically safe to stream whatever data it wants from any source whatsoever to the host.
You can use something like the
Retrode directly to image original cartridges, avoiding the illegality and general miasma of online emulation resources. It also lets you plug in your original joypads.