A few in their own ways.

IX is the big one. It gets a lot of love from this forum but its just pretty much ignored overall, I find. I also think it sold less than VII and VIII and X by a good enough margin, but I could be wrong.

V is sandwiched in between IV and VI which are very loved games and it doesn't get a lot of love.

XII seems to be under appreciated by a lot of people, myself included at first.