It is a shame, because rarely are the sequels as good as the originals. The problem is they write it as one-single story, and then after it is a big hit, people clamor for sequels. But you run into so many problems with sequels. The first is expectations, and then making the story compelling to complete the trilogy.
I believe the Matrix suffered what happened to Back to the Future. The originals of both of those movies are classics, but the sequels, while both very good, were just not at the level of the original. There is only so much you can do with these topics.
The Lord of the Rings succeeded because the stories were filmed all at once, so you had a general flow to the movies. The only movies that defied the odds with sequels that were either better or just as good were The Empire Strikes Back and Terminator 2.
It is a shame for the directors of these movies like Matrix, Back to the Future, Star Wars Prequels, Indiana Jones, Jurassic Park, and many others. People cry for more movies, to continue the story, and when they come out they are held to high standards. Usually people are let down because they have so high expectations, they are never met.
The Matrix was king of the world in 1999, and now it is somewhat tainted by Reloaded & Revolutions. Back to the Future was king in 1985, by 1990, no one went to see Marty McFly in the old west. Finally George Lucas, who many consider a genius, has taken his lumps for the past six years with the Star Wars prequels. I guess they're in a no-win situation.