Since I do not have a rotary joystick, I was trying to play Ikari (joystick hack bootleg) which allows you to move in 8 directions while shooting in the direction you are facing, just like Commando and other shooters of the same genre.
But I figured out that this hacked version is waaaaay harder than the original Ikari Japan version, since it has some other hacks not mentioned anywhere else! It almost never let you to get the first tank at the beggining of the game, it shows the tank randomly but most part of the times you will never see it. Sometimes it won't allow you to get the second tank either (the one on the left of the first stone face). Despite the fact that it has a graphic glitch where you can see your character "walking" inside of the tank while moving it around, which is awkward.
Other thing that makes it hard to play is that enemies will not be aligned to your shooting angles (since the original rotary allows you to fire in 12way and not 8way) so you have to keep "aligning" yourself to shoot some enemies! This leads you to easily die in places where you wouldn't if you were using the proper controller.
After being beaten up by this hacked version, I decided to search for information on how to play the original Ikari without a rotary joystick and I've found a wwebsite where some people made an adjustment to allow you to better play the original Ikari and other similar games without a rotary joystick, and to my surprise it worked like a charm!! And now I'm making some real progress in the game using all 12way on my regular keyboard.
All you need to do is set your controller like this:
Positional Digital Speed = 0
Positional Sensitivity = 100
And map your keypad like this:
7 (rotate left) - 1 step for each key press
9 (rotate right) - 1 step for each key press
8 - UP
5 - DOWN
4 - LEFT
6 - RIGHT
These are my current settings and now I'm enjoying this game even more because it's fully playable with a decent precision! It's not perfect but it is waaaay better than the hacked crap! Here's the link to the original discussion forum where I took the information from: http://forum.arcadecontrols.com/index.php?topic=137631.0