Good bosses are a tricky subject, but they are perfect for RPG's, because of the mechanics of the games. In most of them it's all about power (technically in Planescape Torment too, but the game didn't use a lot of the combat mechanics) and Bosses are the perfect tool to show how powerful you got after X hours of Gameplay.
You don't need bosses for that, regular enemies do fine.
Of course then you do have people who go all "level scale them! I don't want to feel like I've made any progression!!!"