I'm hoping for a pair of phones that might convince me to ditch all the big expensive gear once and for all, but has not happened yet, and I've heard most of the usual top contenders these days plus many a vintage classic along the way.
I have 4 pair currently: STAX, Sennheiser, Klipsch, Audio Technica. All are nice, very detailed, balanced, good dynamics, lots of fun and enjoyable, but can't touch my big rig in terms of sounding real.
How do I know? I can listen for hours on my big rig until I force myself to stop. Headphones fill the bill for awhile but I am always ready to take them off a lot sooner.
Very good for hearing purely what is in any particular recording though. Knowing how different recordings sound in headphones can be a help when it comes time to assess system sound quality because there is so much variability alone just in how various recordings are produced and sound. Think of phones as "monitors". Speakers are needed to communicate the whole deal properly.