This shall be a simple one as there are only two movies in the franchise so far.
Toy Story
The original, the movie that started Pixar's legendary streak.
Toy Story 2
The sequel to the legendary first movie.
Now both movies are really awesome experiences. And to me personally, the difference in quality is such a tiny order of magnitude. I mean it really comes down to what the movie is saying to you.
With that said,
Favorite movie
Favorite character
Line of dialogue?
How awesome is Pixar?