Haze is actually correct, I was initially only asking about bootlegs which emulated functions that were still locked behind unemulated MCUs in the parent sets (whether it's missing sound, broken graphics, or simply the parent set not running at all). I was thinking back to when games like Alcon/Slap Fight, Tokio/Scramble Formation, and others still didn't have their protection MCUs emulated, but had bootlegs which circumvented them and thus ran in MAME. With Caps0ff resuming the decapping effort after recovering most of the lost chips, and general breakthroughs in MCU emulation over the last several years, I wanted to know which bootlegs were still necessary to get an emulation of more of the "complete" game experience than the parent could provide.
However, CTOJAH is also correct that as information has come along about clones which lack emulation bugs that occur on the parent sets, bootlegs/clones which have improved performance due to running on superior hardware to the parent (despite not actually being accurate to the experience of playing a real official board), and so on, I've been listening to those comments too, and am broadening my inquiry. I edited the original post, just so it's absolutely clear that I'm now after all of the above. There's no need for an argument here.