Number Four, singleplayer
Planescape
Planescape: Torment is the best RPG released on the PC, along with Knights of the Old Republic. However, it came three years before Knights and it's a testament to Torment's design that after those three very long years, it's still good enough to stand toe-to-toe with BioWare's latest. Unfortunately, Torment is also one of the most obscure and unpopular games, the one nobody picked up. "It's like Baldur's Gate, but a weird setting", "You can't design your party", and "That perspective makes it look too much like Diablo" are all common complaints. That it was released almost completely after Christmas didn't help much, either. Yet, like Master of Magic, another game almost no one played, we all like to say we played Torment.
Torment was ahead of its time, but unlike Allegiance, not in a bad way. One of the greatest compliments I can pay to the Black Isle team that developed it is that they out-BioWared BioWare. As good as Baldur's Gate II is, few who've played both games can say that it's the better game. Yes, the combat is better. Yes, it sold better. It had multiplayer too, and a great expansion pack. But Torment had the best story of any game, ever. "Flaws" like pre-built characters were strengths as you played the game and discovered the mystery behind the Nameless One and his strange relationship to the floating skull, Morte.
The mystery and the character developments were interwoven with each other and the game world. Even the famed Ultimas (many of which could rightfully argue their spots onto this list) didn't feel as complete to me as Torment. Oh sure, they had their day and night cycles, and NPCs had schedules, but Torment was so clearly a labor of love, filled with painstaking detail. True, it lacked many of the cooler features of Baldur's Gate II, like getting a fortress for your character or the millions of sidequests with their cool gear, but Torment was more focused and delivered a far better story.
It's almost as if it was half adventure game, half RPG. Adventure game is almost a dirty word nowadays, conjuring up images of cheap, tricky puzzles and corny dialogue, but the way Torment pulled it off, it worked. If you've played Star Wars: Knights of the Old Republic, you know exactly what I'm talking about. Up until KOTOR, Torment was without comparison. In fact, the similarities of story development and style between the two are more striking than the differences in game mechanics and setting.
I have little doubt that Planescape: Torment influenced the design of Knights of the Old Republic, consciously or not. Or perhaps the designers naturally moved onto the logical next step, the best ideas, all the things they couldn't do in Baldur's Gate I and II - and those happened to be the same ones as in Torment.
Planescape: Torment is Number Four on FiringSquad's Best Singleplayer Games of All Time for being the best RPG, bar none. If Knights had been released earlier it might hold that position, but it'd be a gamble I wouldn't want to place bets on.