Kasbah - great food (try the Moroccan Cigars) and decent prices, but lousy service, always showing lubavitcher rebbe videos and always incredibly crowded. Maybe a 3.5 for the ambience but a 4.5 for food and prices (prices being Manhattan kosher prices).
Nargilah - Decent food, nothing special, average prices. Maybe a 3.
Colbeh - Lousy food (though my wife loves it) and very overpriced. Maybe a 1. I admit I may be a bit biased against Colbeh (though I always disliked their food) as the one in Manhattan canceled our Shevah Brochus one day before the sheva brochus because they got a "better offer."
Do you mean Darna instead of Kasbah? Darna is Moroccan, while Kasbah is really more deli than anything else. I've only been to Colbeh once or twice and never paid so I can't comment on the price, but I enjoyed the food. Nargila is average food and average price. I enjoy Darna although it's probably a touch more expensive than Nargila.