The Innocent Victim-It's really easy to get behind the main character when he is innocent and was wrongfully accused and sentenced. Some movies that fit into this category are: Hurricane, The Fugitive, Papillon, The Count of Monte Cristo, The Green Mile, and The Shawshank Redemption.
Wrong Place At The Wrong Time-These movies feature an inmate who is not really a bad guy but was just at the wrong place at the wrong time or received a ridiculously harsh sentence. Some of these include Cool Hand Luke, The Longest Yard, Con Air, and Les Miserables.
The Prisoner Of War- These films not only deal with surviving but almost always involve groups of prisoners escaping. Some of these are The Great Escape, The Deer Hunter, Rescue Dawn, Victory, Night Crossing, etc.
The Pardoned Convict-These are movies that involve springing an inmate from jail so he can help the police and be pardoned or receive a lesser sentence. These include The Rock and 48 Hours.
Futuristic Escape-Then there are movies with more figurative or futuristic prisons or confined societies that the hero must break out of like The Matrix, THX 1138, Chronicles of Riddick, or Logan's Run.
Some prison movies don't fit so nicely into these categories like Escape From Alcatraz or Brubaker but they still have the exciting elements of life in prison. I'm not sure why, but movies where the main character has to fight to get free or escape an unjust system have always appealed to me, even if it's a bad guy. I admit that I'm biased and if there is a prison or an escape involved in a movie then I will probably give it an extra star no matter how bad the movie is. At least I'm honest about my bias.