What I liked about Outlaws was:
* The cartoony style (amazing for an FPS, and still unusual)
* The use of sound (as you walked through the town your enemies would taunt you, and you could follow their voices, though that can be misleading. The soundtrack is also one of the best of LucasArts)
* The fact that it had a strong LucasArts storyline and a few puzzles despite being an FPS.
I was so used to Quake at the time that Outlaws was very refreshing.