I'd say that it is not. Given the reasons people generally cite for it's possible place as "Best RPG Ever" (the narrative and characters), I'd say it wouldn't qualify as Planescape: Torment wins in this regard as far as I am concerned. That said, the Baldur's Gate saga is a bit more mechanically sound throughout where Planescape tends to be a hair too easy at times thanks to rapid leveling and absurd stats by end game. Hell, by the end of Torment, I could call down apocalyptic magic, restore shattered armies to action and single handedly wade into a vast hoard and slaughter all that stood before me.
Of course, one does become fairly absurdly powerful by the end of Baldur's Gate as well but not nearly by the same margin.
Of course, one does become fairly absurdly powerful by the end of Baldur's Gate as well but not nearly by the same margin.