Its depends on individual perceptive
Love is known for the beginning of Human origins still we don’t know how it works .So love movies tend to be a certain pattern and the outcome will be two .Either they will unite or they will be separated .The emotions behind them are really complex and no science can explain this
Science is a continuous evolutionary process .Every year new achievements will be in science and once the formula is decoded it is finished and it can be used as exactly as per the formula in technology devices which our lives based on .But scientific movies will lead to many outcomes .
Take an example like time travelling -the outcomes of movie can be – what happens if we can travel in time ?what happens to present self?can future changed?how the future self will behave now?are there any complications happens in time travelling what will now ? etc some of movies of scifi did good job in predicting most of future events and at that time these movies did nice job
So finally I feel scifi movies are interesting to watch because of many outcomes of story involved