Best headphone to date: The original Jecklin Float.
just got the new Shure 500s...significant improvement over 5c, 4c etc. 5c has that bass thing going but 500s are tighter and better attack: mid range is more clear and open sounding: treble sounds more extended though may not be true: but overall the best in ears I've heard: that includes the 2 other Shures, Etyomic 4s and untimate ear pro 5.
There is not a "best" for me. There are several top-line cans for I use depending on what kind of music and how the recording sounds. I use Audeze LCD-2 w/Burson HA-160 headamp for "perfect" recordings. The beyerdynamic T 1 w/Burson HA-160 for jammin' rock and roll with good bass in the recording. Sennheiser HD-800 balanced into Headroom Balanced Desktop/w desktop power supply when I want to hear exactly what is on the recording. Westone 3 IEMs are my overall preference for portable listening into a HiFiMan HM-801 PMP.
Etymotic headphones tend to be a bit analytical in my opinion. I have some er4ps I use for the gym and have had the er4s... I bought my wife a pair of the ER6is when they came out which should be around here somewhere.
The isolation is great and its better then nothing on a long flight, but they don't really keep my focus.
The Ultimate Ears mentioned in the thread are a little less analytical, but a little dull IMO. I'd scored a couple pairs of the TP10s when they were blowing them out about a year ago, but I ended up just gifting them to friends as they weren't my cup of tea.
The Grado in ears look interesting, but I haven't heard them yet. I've owned most everything Grado made (Joe and John) over the years and though many hate them, I found them to be generally musical, warm, detailed, a little flat stage wise, forward in balance.... Thats one I'd investigate personally.