Ooo, I just ran across this article on Topless Robot and it was too good not to share!
I totally agree with some of them – the Slave Lords, for example! And Strahd, Lolth, and Sakatha are good choices. Some of the rest are weaker, though, it seems like they’re sticking hard to 1e AD&D for the list.
Some of my picks? Well, you can’t leave off Bargle, even if (until recently) he was more implict than explicit. And for more Basic fun, the Master of the Desert Nomads was a fan favorite hereabouts.
2e’s harder. Although if you play your cards right you can fight Orcus! A lot of these, especially the Greyhawk ones, tended to be sandboxy so there’s not necessarily “end bosses” – like Rary’s stats are in Rary the Traitor but I’m not sure he really counts as an end boss there.
In 3e, the WotC adventures blew chunks, but there were still some excellent end bosses out there. Sea Lord Drac from the Freeport Trilogy, for example. And the end boss Xanesha from The Skinsaw Murders, second chapter of the Rise of the Runelords adventure path, is hated and feared by many a PC party.
And, of course, there’s Invisible Christopher Walken!
Who are we forgetting? Who are the boss end bosses? And why are there so few, especially post-1e?
Geek Related 
Well, I’m assuming that the article skews to 1e because it’s what the author knows, and was the edition where the modules were king.
As for other end bosses, you’ve got Bargle right, but of published adventures I’ve run and played, I think Dragotha and Kyuss from Age of Worms should get a mention. Dragotha especially–he’s not the end boss of Age of Worms, but the build-up treats him like he is, and he was a much tougher match-up for my players.