I had the LCD-2's before the HD650's.
"Best headphone" is a hard term to use. I have no idea if the HD650s are the best headphones. All I know is I sold my Audeze rig, and thus far I don't regret having done so. I could see myself with some Audezes again someday if I ever have money falling out my ears, but I can't say I wish I'd kept them.
Obviously stacked point to point the HD650s can't beat the flagships. But there's a weird thing that starts happening: the Audeze were SO detailed and SO high quality it was like I was listening to the headphones, not to the music any more. I'd wager that effect only worsens the higher up the scale you go. I found myself trying to find recordings that maximized the Audezes rather than picking music I like. Not a fan of that.
The 650s are in this really sweet spot where they'll do whatever you need, but not more than you need. No genre sounds bad with them, even if they don't shine in one or another the way others do. They're a jack of all trades, even if they're not quite a master of any of them. They're the rare headphone where I feel like you can go "it doesn't matter what kind of music you like, these will work." They're not prohibitively expensive, they don't need the perfect amplifier (although they scale), they have a great fit, they're not heavy, they look sharp, are great for gaming as well as music... so yeah. In a way, I can see why they are "the best headphone".