I'm getting ready to order either Daisenpu or P-47: The Freedom Fighter and I'm looking for a game to get with it. Something especially cool, preferably within the $20 range. I'm eyeballing Space Harrier (I have yet to own/play a version of it.) Neutopia is also a possibility. Any other suggestions? I'm on a side-scrolling platformer kick lately (including run & guns and possibly beat-em-ups.)
Well, not knowing what you already have and sticking to PC Engine only, I'll through some out there for you to consider:
(Some of these are the basic side-scrolling platformers that you should already have or know about.)
Ankoku Densetsu (The Legendary Axe II)
Cadash (PC Engine version shouldn't be too expensive.)
Chozetsu Rinjin Berabo Man (Bravo Man)
Fushigi No Yume No Alice (Alice in Wonderdream)
Kaiso Chojin Schbibin Man
Kaiso Chojin Schbibin Man 2 (Shockman)
Kaiso Chojin Schbibin Man 3
Kato Chan & Ken Chan (J.J. & Jeff)
Kiki Kai Kai
Legend of Hero Tonma (I've seen the PC Engine version for $20 or less recently.)
Makyo Densetsu (The Legendary Axe)
New Zealand Story
PC Genjin (Bonk's Adventure)
PC Genjin 2 (Bonk's Revenge)
PC Genjin 3 (Bonk 3: Bonk's Big Adventure)
Son Son II
Takahashi Meijin No Shin Boken Jima (New Adventure Island)
Valis
Valis II
Valis III
Valis IV
Valkyrie no Densetsu
Wonder Boy III: Monster Lair
Yokai Dochuki
Ys III: Wanderers from Ys (more of a side scrolling platformer with RPG elements - PC Engine version should be very cheap)
I'm sure that there are many more, but the above are some of the ones that I am familiar with that I feel are good and should fall in (or near) your price range.