Depending on whether or not you have the horsepower to run them, NAOMI vertical shmups are awesome.
I'm using Makaron T12/5 to run them (some newer builds aren't as compatible)
It's running on a 2.9Ghz Athlon X3 triple core.
There is some slowdown, but it isn't too bad.
You might try Demul. It's a lot easier to set up.
I didn't use it because the games had issues going fullscreen on a horizontal monitor, which won't be a problem for you.
There are the vertical Taito Type X games that have been cracked also.