Nice use of the theme. I like how switching between the two roles forces you to heal and keep the Jims alive whilst you are alive so you can stay alive as a ghost. It would be interesting if you could interact with some more things as a ghost (e.g. the bullets the ghosts fire do 'damage' by decreasing the timer, or you could push ghosts away from Jims if you are a ghost).
The music was good, but moving on the platforms felt a little too slippery. The game might need a bit of tweaking with the enemy spawning, since ghosts can spawn close enough to a Jim that dealing with them is pointless.