Number 6
Knights of the Old Republic II: The Sith Lords
I have a thing for forgiving games of their flaws when certain elements are superb, and no game on this list exemplifies that ideology better than this game right here. There are two parts to that: this is the most deeply flawed game on the list, but it has the single most outstanding quality in a particular area, which lifts the entire package up into the stratosphere.
The flaws are easy to think of and easy to list. In many ways the game is broken, full of enough glitches to make BioWare or Bethesda blush, with missing mission flags and bugs galore. The leveling system's cap has been removed, making all challenge in the endgame utterly trivial, and there's this sense of emptiness there, at the end, which left many people dissatisfied.
But you know what? It doesn't matter.
There is at least one thing this game does well, and at that it's the very best in the business: writing.
In KotOR2, Chris Avellone forged white-hot the most consistent, thematically tight, mind-bending narrative I have ever experienced in any game, a plot which would stand proudly as proper literature if it were not in the trappings of Star Wars, a story and characters that are simply the best that this medium has ever produced.
You want the best cast of characters? Right here: from Atton to the Handmaiden to Darth Sion to T3-M4, every single character has their own motivations, their own secrets waiting to be wrested from them. They are believable, complex, alternatively weak and strong, each wounded, each hopeful. In any other game they would be the stand-out members of the cast, but each of them is only a single piece of the puzzle.
You want consistent meaning and theme? THis game got me and my wife talking for hours about Nietzsche, how one character in particular basically symbolizes him, how different philosophers would shape themselves in the face of the reality of the Force, and that's only the most basic, surface-level stuff. Themes of maternity and paternity run through, betrayal and family and what it would take to change the heart of a man, the constant struggle for power in the face of personal weakness. It's good. It's really good.
What's more is that Sith Lords has, in Kreia, the single best character that video games have ever produced. Kreia is the mentor character, a sort of inverse Obi-Wan Kenobi, and she is far and away the most complex and engaging character ever birthed by that continuity. I won't say what makes her so great; on some level I hope that a person will read this and decide to play it for the writing, because they should.
This game is something of a crippled god. It has a limp, a set to its bones that isn't quite right, but when it flexes its power can shake the foundations of the world.