"What can change the nature of a man?" Let the search begin!
Yes, it is an old game and the graphics are dated. Planescape: Torment runs at a resolution of 640x480 and is powered by a 2D graphics engine (Infinity, the same engine that powered Baldur's Gate series and Icewind Dale series). For some, that might constitute an insurmountable problem, if that is your case then I pity you. The best way to approach this game is with an open mind.
Among the first things you will notice is the unusual level design: a lot of metal and stone, many sharp shapes and many arches and archways. This "look" can be found almost everywhere in the game environments and creates a very coarse feel. It serves as a complement to the overall theme and adds to the immersion factor. Sound and music also play their part in this and both are great. Actually, Torment's soundtrack is probably one of the most breathtaking soundtracks you'll ever hear, no joke! It's such a strange mix of orchestrated melodies, tribal beats and electronic effects, do not play the game with music turned off!
But the thing that contributes the most to immersion is the writing. You'll have to keep your eyes on texts most of the game's time, offering a level of immersion that only a book can offer. The story takes off with you awakening on a slab in a mortuary with nothing but the scars on your back and a talking skull starring curiously. You begin a quest of self-discovery that is crafted with incredible attention for detail and full of memorable moments. Your journey will take you to some strange places as you retrace your past and depending on your actions you will also leave a mark on the world. That's one of the remarkable things about this game, the world is not static, NPCs respond to you differently and there are many situations that can be handled in different ways. The characters you meet are also one the best aspects of the game: it's easy to get attached, each and every one of them has something special, something unusual about them. Also, I've heard people saying "the end is bad, it sucks etc"; I can tell you that there are multiple endings and they reflect your character's emotional stance and choices and I can also assure you that Torment has a proverbial "grand finale"! It's also worth noting that this game breaks a lot of cliches, even death is handled differently here.
But what of the gameplay? Sure, Planescape: Torment is an unusual game but it still uses the Infinity engine which means it is somewhat similar to Baldur's Gate. You don't have as many customization options here but to be perfectly honest, who cares about customization when you've got atmosphere and writing like this. You begin as a fighter class but you can change it by seeking a teacher: you can remain a fighter or you can also choose to become a mage or a thief. The weapons are also unusual, you can fight with bones, with big talons or with huge axes, but no swords (cliche-breaker element). Also, there are no ranged weapons but you will not need them, specially if you play as a mage. The combat might not be the best you'll ever encounter but the multitude of dialogs and dialog options, coupled with a fascinating setting and a masterpiece of a story make this game one of the best ever made.
It's no use carrying on about how amazing Planescape: Torment is, you have to play it for yourself to see. So my advice is this: if you like a game with a great story or if you like RPGs then play it... and after you do, maybe you can tell me what can change the nature of a man.