In my opinion these questions are almost universally subjective and don't bring much value to the site. It is very difficult to answer whether and which of the predecessors are mandatory to understand the story. Video games are a more self-contained medium than books and films and games in which gameplay mechanics can't be effectively learned by starting from a sequel are few and far between.
The best example I know is this answer (+20/-1 votes) to "Do I need to play previous Witchers before Witcher 3?" question:
The Witcher 2: Assassins of Kings I highly recommend, great story and you make some big decisions.
The Witcher is a bit old now and the controls can get a little out of control so I would advise you to check a synopsis online.
As you can see, he recommends skipping the first game in a story-driven series and doesn't provide a meaningful explanation to why the game is best avoided.