Soylent Green I found to be an excellent movie.
If you like Logan's Run you'll like this.
Yes the movie is old and there are no special effects and some of the acting can somewhat be best described as "cheesy" but the story is excellent.
The story of how the world can be and its impact on society is very poignant.
At the end the mystery wasn't a mystery but the story unfolded in an easy at the right pace.
It's nearest modern day equivalent would be "Dark Angel" in terms of how the US is shown to be third-world country.