Knights of the Old Republic is, from action-packed start to revelation-filled end, the best video game I've ever played.
I'll start with the voice acting. I don't even want to know how much time it took to record all of the dialogue in this game. There is a massive amount of it, and all of it is spoken. When playing without subtitles, it added about six or seven hours to my gameplay. The voice actors and actresses are extremely talented. It's very interesting to listen to your party characters reveal their past, particularly Carth (if you are a female player) and Bastila (if you are a male player).
There's a lot of different action styles to use with your different players. There are some characters, like HK-47, that provide ranged support with blaster rifles. Other characters, such as Bastila and yourself after you become a Jedi, are much more focused and lightsaber combat, providing a unique mix of combat features. There are several different feats to use, both for swordplay and for gunfire. All of these feats upgrade from Basic to Improved to Master. Not only are there different styles of combat, but there are also many different Force powers. Most of the light side powers are supportive in nature, such as Heal or Cure. Almost all of the dark side powers are malicious, with the most deadly being Force Storm, a storm of Force Lightning that hits every enemy in range.
There are seven different distinct worlds to which you travel. All of them are very unique. Manaan is very peaceful on the surface until you go under the water. Tatooine, on the other hand, is a dry and barren wasteland. The artwork for all of these planets is very unique. There is a different style for every planet that you visit. Taris is a planetwide city, Dantooine is peaceful grassland environment, Tatooine is dry and sandy. You get the idea.
The quests in the game are very engrossing and unique. There are some sidequests that are very quick and only require one of two actions. However, there are others, such as Sunry's Trial on Manaan and the multi-world Genoharadan Assassin Guild which require many different actions and can take up a lot of time. The main quest of the game is very engrossing and it plays out just like a Star Wars movie. When you near the end of the game, there will be a massive revelation that I won't spoil, but it turns the game on its head and makes the whole thing worthwhile.
There are nine characters (ten including yourself) that you will control throughout the game. Each character is very unique and has their own strengths and weaknesses. Mission Vao is excellent in stealth and should be used as such. HK-47 is the perfect ranged support character, as I said previously. Jolee is excellent to give dark side powers to if you are light side, since he is neutral. Every character is extremely unique and each one is different. However, there are some that you will most likely never use again in the game. I myself almost never use T3-M4 or Mission Vao, but that will happen with all who play this game.
All in all, Knights of the Old Republic is an utterly amazing gaming experience. I have played the game all the way through three times and every time I play, something new happens. You also have the feature of choosing your own destiny, which allows for two different game endings. Of course, I won't tell you what those game endings are, but both are very satisfactory for your gaming style.
All in all, about 1000/10. Best video game. EVER.