The Bose Quiet Comfort II noise-cancelling headphones are the best of the bunch, and also the most expensive at about $300 US. I absolutely love these things. A nice big cushiony ear pad helps with noise cancelling and comfort on the ear, the pad on the band helps with comfort on the head, the sound cancelling doesn't give me the "high pitched ringing" that the Sony does. The downsides are that it's the bulkiest of the lot, the 1-prong to 2-prong converter will surely be lost, and that the sound doesn't pass-thru on a dead battery. CNET Review.
Second place, which we also have, is the Sony MDR-NC20 Headphones. They are decent, with a really nice and small form factor and the 2-prong converter folds into a 1-prong converter. I found they bothered the top of my head and my ears got irritated with a high pitched ringing after about 5 hours. They've dropped a fair bit in price, from US $179 when I bought them a year ago to $110 now. These are a good deal if you don't want to shell out the big bucks for the Bose.
I was really wanting to try the Etymotic ER-6 or ER-4P earbuds, but I never had the chance. I also listened to the Sennhauser and Panasonic models, and they weren't worth it.
I think that if you do a lot of travel - like over 30 000 miles a year - it's only really worth getting the Bose. If you are doing less travle, it's probably not worth getting any headphones as they can be a hassle to carry around.