Whoa, that's an impressive list, and you got almost all of them right. Great job, dragon dude! I'm not going to spoil all the fun by telling you what the question marks are, but I'll at least tell you which ones you got wrong.
Oh, and one thing to note is that some of our parody titles take inspiration from more than one real-world source.
Dude Shinobi = American Ninja
Dude Shinobi is mostly inspired by the American Ninja franchise, as you've guessed, but he's also inspired by a couple other action stars. Two in particular.
Double Dudes = Double Dragon
Partially correct. Double Dudes vs. Satan Ninja is a combination of Double Dragon and another arcade game.
The Eternal Departed = The Grateful Dead
This one's wrong. But I can't blame you, as the real-world band that inspired The Eternal Departed is
extremely obscure and is one of the only (in fact I think it's
the only) parody name that isn't inspired by something from the '80s ...
Horrific Holiday = Halloween
Partially correct. It's inspired by the general trend for horror films to always be themed after a particular holiday or special date (Halloween, Silent Night Deadly Night, Friday the 13th, April Fool's Day, New Years Evil, My Bloody Valentine, Happy Birthday to Me, etc.)
The rest you got spot on.