Yeah those might be hard to emulate, since usually you need the real hardware (since it generally only does one single game). From experience, though, a lot of late '80s arcade systems produced sound like http://albion.bandcamp.com/track/fly-without-fear (although with crappier instruments). Not sure how old the Capcom arcade systems are, though, since when I was kid I only went into an arcade once (I think it was in 1994 or something), and my mom didn't like it because of pedophiles roaming there. (I think this is why the arcade was closed down)

That sounds quite nice

So far: The newgrounds stuff is good, but reminds me more of the 16 bit era. I really like Hills, and Rockin your nes. Really good nostalgic tracks there. =D Neonbridge is very nice and nes-like as well. Reminds me a bit of balloon attack, or some of the Mega man to stuff with your drums.
Work in progress 2 is kind Genesis-like, but is a bit too busy IMO. Sometimes it sounds like there is too much going on, and some of the instrument levels could be adjusted so you main melody isn't being over run by the rhythm/background. I still really like the overall sound of the track though. I'll edit and add more thoughts after I look at and listen to the stuff on page 3. =)

*Edit* Ok, the spaceman remix is great. The most recent one you posted may need some adjustments on insturment levels, but not too bad otherwise.

Sounds pretty cool! As you said drums might be a bit too loud, but it's not really a big deal on that track. =)

Part of the drums is generated by the computer since the drums on my synth are pcm and they sound do not that great. It's a cheap FM synth with late 80's drum set

Aaaand a remake of an 8bit song I made a long long time ago (I can still remember; that music used to make me smile)
http://soundcloud.com/koenvanvliet/pharaohs-nes-remake

Thank you, DJ. I'm working on a chiprock album at the moment