As much as I like it the Neo Geo was far from a mainstream console
I would still put it in there, remember the pc engine was only released in Japan, so it was only mainstream if you lived there
Erm . . . .
PC Engine was released as the TurboGrafx 16 in the US and got a limited release in Europe as the TurboGrafx, hence why its included as the PC Engine / TurboGrafx in this poll
The Neo Geo sold in small numbers to home users and was never available in any shops that I know of.