Okay so let me introduce the two. 

Lost is a TV SHOW about a couple of friends on a plane ride and they crash land into a island and they have to survive and try and look for help. 

Castaway is MOVIE starring Tom Hanks were he is on a buisness plane trip and the plane crashes into a island and he has to find ways to survive and look for help. 

Excluding the fact that in Lost they are a group of friends and in Castaway he is alone, aren't they the same thing? Except one is a tv show and one is a movie? Because I watched Castaway and decided to watch Lost. And in my point of view, they are the same exact thing. I mean that is just my opinion.