Those patents and laws that protect the games don't really exist in the countries where these things are put together (and are LOOONG since not applicable in courts of law regardless due to the time on the patents running out). Many of the 'commercial', especially disk driven, ones I've played had long loading times, poor emulation, etc. Much of the Neo Geo library IS faithfully reproduced in those Elf carts and such. I feel like the original Neo Geo multicarts are the basis for these expanded ones. Someone just saw how much they could tack on after the fact and ended up with a mix of anything from acceptable to shoddy. Put a Neo Geo X or (and this is just plain WRONG!) a PS2 SNK Classics disk next to one and watch the HORRIBLE and TOTALLY UNACCEPTABLE frame rates and music that THE COMPANY THEMSELVES SOLD TO YOU! The only way much of the Taiwanese hacks of the Street Fighter games are still around IS because of these Chinese multicart makers like the ones who brought us "Just Another Pandora's Box" or the "Blue Elf" series. Games where fireballs have wave patterns or you can jump and do tornado kicks that disappear and reappear all over the place. There are a LOT of manipulated and hacked up versions that have unique changes that seem to reflect what was done later in sequels.
Now that I see you are most likely only referring to the 'Games Family 60-in-1 Multicade' I am reminded of the day I bought my two cabinets. The dealer said that they burn up those HD ones all day long and that he's pretty sure ALL of them are 'pretty much not legal'! Even the Multicades. AND, there are different quality issues with different versions of that card as well (later, cheaper versions I guess). I asked him if he'd ever heard of the "Blue Elf" series and he said, "No, and those might not be illegal because it's made for China.". This was a guy who's been dealing arcade cabinets and 'upgrading' them with hard drive based multicarts since the beginning!
I bought my cabinets unaltered and did the work together with my wife.