Bananasaurus_Rex is easily one of, if not the, best Spelunky players out there. And right now he's in the middle of an incredible run to rack up a record score of $3 million, which means getting every single piece of treasure in every level.
UPDATE: He broke the record, and hit $3 million, a score that isn't likely to be topped any time soon, if ever.
He streamed for ten hours before breaking the record, attempting to get everything just right. To get this high score, he had to break out every trick in the book. It basically makes this the opposite of a speedrun, as he slowly broke every block in Hell to get every last bit of hidden treasure.
Here's the moment when he passed the previous highest score:
And here's the big ending, when he broke $3 million, and beat the game:
This run is impressive not only because it requires so much skill, but there's also a huge element of luck involved since all of Spelunky's levels are randomly generated. Somehow, against all odds, he managed to get a level where he ended up with a plasma cannon in the very first level, and a jetpack in the second. That let him fly around the ghost while it turns gems into diamonds, and blow up entire levels without running out of bombs. To put that in perspective, I've been playing Spelunky for months, and have never even seen a plasma cannon, especially not in the first level!
So, for someone to beat this score, they would have to go through everything Bananasaurus_rex did in this run, including the impossible luck of the plasma cannon on 1-1, but that still wouldn't be enough. They would also have to have one more Kali altar generated that, if they destroyed it, would summon a ghost at the beginning of Yama's lair. That would allow them to turn those final rubies into diamonds, increasing their value. My guess is that it would take a lot more than ten hours before someone got that lucky.
You can watch the whole run on the archived stream here (skip to 03:29:00 for the beginning of the final run):