Trojan kind of sucks. And by kind of, I mean a whole lot.
Mach Rider is somehow worse. Although I'm not a fan of racing games where it basically looks like you're sitting in one place while the terrain itself moves, so that's just me.
Rygar is a wonderful game!...If you're using an emulator. Good luck trying to get through the whole thing (let alone killing the final boss) without save states.
POW is a pretty good Double Dragon rip-off.
Journey to Silius is kickass in every concievable way. If you're using an emulator, rip the entire soundtrack.
Life Force is a great side-scrolling shooter.
Flying Warriors...eh. I remember hating it as a kid, but I played it again recently and it wasn't too bad. If you like Secret Scroll: Flying Dragon, you'll like Flying Warriors.
Dude, Duck Tales...don't even need to ask with that one. Play it. Immediately.
Image Fight is quite possibly one of the worst Galaga rip-offs I've ever played.
Guardian Legend is one of my favorite NES games. It switches between Galaga-on-crack stages and Zelda-style exploration.
Gyruss is probably my favorite arcade shooter for the NES. Why? I dunno, I just like it.
Dynowarz.....why don't you just see for yourself?
Castlevania III? Is this a rhetorical question? PLAY IT.
Code Name Viper is a complete and utter rip-off of Rolling Thunder. So if you like blistering difficulty, it's alright.
Blaster Master, hellz yes. An underrated Metroidvania-style game.
Battle of Olympus, also a good Metroidvania game, but be prepared to use save states; the game uses
enormous passwords.
Astyanax...don't bother. Trust me.
Amagon is one of the worst games. I've ever played. It's easily the worst Contra rip-off I've ever played, and it's just...so...mundane.
Captain Comic is a waste of my life. If I press the A button, I really expect my onscreen character to jump within three seconds of the press. Not so with Captain Comic.
The other ones I either haven't played or haven't heard of.