This game was so enticing and suspenceful! Though, with some tweaks, you could turn this into a real classic and probably make a little money off of it. This is why I think so (SPOILER ALERT!):
The game does get repetitive once you've figured out a lot of it, replay value becomes null eventually. The ghost(s) don't make you jump anymore, they make you think "oh damn.. one of these floors again". Dropping one floor makes it able to beat the first floor, all the awesomeness of the lower floors will not be experienced once a player figures this out.. So I had this in mind:
Needing an item (key, axe, maybe pulling a lever) to unlock the an exit. This should be placed at a random floor or floors. This is a challenge that will not get old, and will make every new game exciting; "Where will the item be? I hope I won't have to go too deep.." Also, one random monstrosity or maybe a zombie or two (that's up to you) could be placed on random floors.. With weak senses so it's not a 'game over' once you catch a glimpse of them.. Once one of those is met and it has seen you, having to shake it off will add a huge claustrophobic factor to the game. Footstep sounds and growling will make more sense in the game then.. + they could actually be realistically implemented by making them weaker or stronger depending on how nearby such a monster is. To not make it too hard.. You might have to get rid of the ghost and tweak some other things.
If you'd do that, I'd definitely pay for that game and I'm sure others would too.
As far as Newgrounds goes, this is still a 5/5 to me, even if there is room for making this a classic!