I ended up playing the Gameboy port
of this game before the arcade original, and found that one OK but kinda underwhelming. The arcade original is definitely more impressive and a little more fun to play, though I'm still left wishing a little more had been done with the concept.
If you're new to the whole deal, the game opens with the Batman-esque murder of our protagonist, gunned down in an alley in the midst of bringing home baguettes. You come back as a spirit, however, and are quickly contacted by a paranormal researcher who clues you in that the mob is messing with paranormal powers for evil purposes ... also they kidnapped your girlfriend and locked her in some tower for some reason.
Anyway, obviously we're off to save the girlie, but we're hampered by the lack of a corporeal form. Fortunately, our intrepid little ghost can possess anyone who is nearby and take control of them. You'll use this ability to hop between enemies and fight them with their own weapons and such. You start out by choosing from a hapless ninjer, machine gunner, wizard or supergirl and then off you go.
The place where I'm most disappointed by this is the fact that you can't switch bodies until your current body gets beat down and dies. So there's not really like a strategy/puzzle aspect to your possession, nor can you even just hop around for fun. The only strategy to the game is intentionally getting killed off near one of the rarer enemies and maybe burning a quarter so you can take possession of them. Your ghost has very limited mobility and your health depletes very quickly when you're not in a vessel, so you're pretty much forced to hop to whoever is most convenient when your current shell bites it.
Setting that issue with the concept aside, though, the gameplay is actually very solid and enjoyable (much better than the GB port, mostly due to larger sprites and more screen real estate to work with). There's a little touch of Shinobi to it in the enemy layout; lotta projectile dudes bunkered down that you have to do a little clever jump-attacking to get at while aggro goons may appear and rush you from the side of the screen at any time.
But there's also a non-linear exploration aspect to many levels, as thorough exploration of little side paths often rewards you with bonus points and life boosts. Rescuing the girlie (to get the best vessel and the Good End) also requires you to find the three keys to her tower door - the first is thrown right in your path, but the last two require a little exploration off the beaten path of later levels to find. There's also a trade-off between power and speed with the enemies you can possess; heavy hitters like the dragon tend to have poor jumping, which closes off some of the optional pathways to bonus stuff, but the enemies with lighter weapons have crazy ups.
Generally good gameplay and good level layouts pair with good aesthetics to make this one more enjoyable than most arcade platformers. There's a limited amount of enemy types, but the sprite work tends to be pretty nice, especially the facial expressions. Quite a decent little chiptunes soundtrack too.
It's a shame this didn't get a port or sequel to a 16-bit system with the full treatment to really develop on the possession mechanic, but this one is definitely worth a play.