Your monitor can't tell whether the game is vertical or horizontal, so it's impossible that all horizontal games work while all vertical games don't. It's a matter of video modes after all. If it's vertical rolling, chances are the vertical refresh rate is too low for those modes. Usually this happens when you try to push too many lines, e.g. 288p for Galaga, then the only solution is to lower the refresh rate to something around 52 Hz. Most TVs would show that refresh without issues, others might not.
If that's the case, the solution is to use a custom crt range like this one:
monitor custom
crt_range0 15625-16200, 49.50-65.00, 2.000, 4.700, 8.000, 0.064, 0.192, 1.024, 0, 0, 192, 248, 448, 496