I was actually going to bring up I Am Legend and its three film adaptions in the "remakes" thread, but things were so bogged down in there it didn't seem to fit into any of the discussion that was going on.

The basic point I was going to make was, can you really consider those remakes of each other? Or are all three independent attempts at adapting the short story to the screen?

Each adaption takes a few details from the book, and tosses the rest out.

The Last Man on Earth was by far the most accurate to the source, but it changed the vampires to zombies.

The Omega Man kept only the premise of the immune protagonist in a world filled with infected night walkers, this time they still kept their mental state intact, but could no longer walk in sunlight and nonsensically got the uncontrollably urge to join a cult. Although the movie is one of my all time favorites simply because it uses the line "honky paradise", which may be the greatest line ever captured on film. If you watched The Last Man on Earth followed by The Omega Man, you might not even realize they were related beyond the single lone protagonist angle.

I Am Legend took the lonely isolation aspect of the source material and ran with it. I felt it did rather well with this, but left out just about anything else that tied it to the source (other than keeping its title, while completely botching the significance of that title). The CG infected just came off as extremely silly.