[toast0]

There's a fair number of low game count systems where people are really enamored with one game. For example, I'm a big fan of T-Mek (I've got a machine with issues in my barn), but that system only has two games, so it waits for someone who is interested, determined, equipped, and skilled to figure out the protection to enable it to run properly in MAME.

[mrandish]

Indeed. With most of the more well-known, higher volume arcade hardware platforms now pretty well emulated there are still a lot of lesser-known (but still quite interesting) systems unemulated. Various people have put effort into most of them but they can be challenging puzzles.