There's still some good ones left.
God of War
Bayonetta (and every other PlatinumGames title)
Devil May Cry
Ninja Gaiden
Kingdom Hearts
The Legend of Zelda
Metroid
Most games are just copies of each other nowadays, developers lack the creativity to do anything even slightly unique or different. So if a game is successful there'll be an army of shitebags waiting to cash-in on it. And I think that's why the majority of modern boss fights are uninspired garbage.