What idea for a novel should I use?

I have enough time and could write a novel. Maybe it's time to just do it. But which of the ideas that pop into my head should I implement?

Preview

1. A modern version of Puss in Boots

A young man inherits a tomcat. The clever animal helps him to luck and prosperity.

2. Love is not rational

An overly cerebral man falls in love with a headstrong woman who doesn't think she's attractive.

3. A modern version of the Golem story

A computer scientist creates an artificial human who surpasses him and becomes his superior.

4. A ghost is looking for his murderer

A man is murdered, but before he is drawn into the afterlife, he has the opportunity to find the culprit as an invisible ghost