Ok..another best of list, this time for the PC Engine! These are some of my favorites....and I've played a LOT of PCE games!:
Sylphia - If you can afford it, an amazing vertical shooter, fantasy style. Great anime cut scenes, good gameplay, a bit easy, but they make up for it with demon breasts on one of the bosses! Great game, lots of fun, but VERY rare!
Castlevania Dracula X: Rondo of the Blood: IMO, the BEST Castlevania. Awesome level design, tons of hidden stuff, multiple playable characters, amazing soundtrack, highly detailed graphics! I love it, and I've never liked another Castlevania more! Some people say SOTN, but to me, Dracula X is the pinnacle of Castlevanias!
Image Fight 2: No one likes this but me. I know it's true and I love it anyway. One of the hardest shooters out there, it's a vertical shmup with great graphics and sound, just UNBELIEVABLY hard. I got to level 7 once. It took NINE hours of straight play. Not for the weak, but very very cool!
Download: Hard huCard shmup, classic side scroller, great Engrish! I especially love when you continue, cause every time it seems like there's a different profane phrase like "I will not fuck this up" Cool game!
More recommendations? Throw em in! This is one of my personal favorite systems ever, but these are just the VERY top few games I love for it!