All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
What you mentioned about the games and fictional novels about matters in the past or the future does not necessitate the prohibition by itself. Rather, what can make them prohibited is when these fictional matters involve Islamic violations, such as claiming some of the characteristics of Ar-roboobiyyah (the Lordship of Allah) or Al-Uloohiyyah (The divinity of Allah; which means that Allah is One and is worthy of true worship) or other matters that contradict sound creed and belief.
In any case, playing with games that include what contradicts the belief does not necessitate, at all, that the one who plays them becomes a disbeliever, as long as he believes that they are false and he does not believe in them.
Finally, we advise you to avoid whispers and not pay any attention to them.
Allah knows best.