but I really don't like the bonus rounds
What?! Ohh man, that was one of my Favorite parts... throwing mass Shrikens at Ninjas!

I almost always fail... but its really fun trying.
The thing to remember on the Bonus stage... is that there is a delay between fire and hitting, because of the far depth of travel. So, send rapidfire sweeps across an area ahead of the Ninjas... and usually it will end up hitting them. Dont wait, and dont 're-sweep', unless maybe in 2 secs your sweep actually failed. If you try to pinpoint them... and or wait for things to hit... you will waste too much time, and lose to the rest of the swarm. Even if you miss a few.. you usually get a 2nd or even 3rd shot at a sweeping them up.
you really need to know what's coming or you're toast
This is Definitely one of the biggest challenge of Shinobi. Move only in small increments, especially in the latter stages... or you will trigger too many Ninjas to attack. By triggering only one or two, you can usually do ok against them. But try to rush too far... and 4 to 6 ninjas will be on the screen at once, slashing you to bits.
Even if you memorize the spots... its often easy to have a memory lapse... or make a mistake because your trying to rush things. Still, even while frustrating at times... its good fun. Def. less frustration than Ghouls and Ghosts... but they are pretty close.. and G&G is a bit more graphically exceptional... which eggs you on.
Older Sega arcade games tend to reuse a lot of graphics... making things drone on a bit.
The best is when you collect several children in a row without getting hit... and you actually power up your weapons.
You can also often jump on certain characters, without then hurting you. It can help at times.
Fire ahead often... even if you dont see anything.
Use Ninja Magic in tough spots, such as a bunker of enemies grouped together... Unless you are really good at getting past them. Then you can save it for the bosses.
The worse boss is probably the spinning Idols. OMG its difficult. I think its often mere luck that Ive beaten it.
(and Ive totally forgotten how by now)
Im not sure if Ive ever fully beat Shinobi. I had the Sega Master system version beaten... but that had far less levels.
Revenge of Shinobi is awesome (",)
I do agree

Should have and could have actually been an Arcade game. A Really well made game.
I guess it probably was easy to me... cause I used the Infinite Shriken trick. Totally forgot about that.
Without that trick... the difficulty is probably decent. But still.. its not as quickly unforgiving, as Shinobi.