Designing Fun Games

In our journey into game development, we've explored a bit of video game history and genres. We've created some interesting concepts and prototypes, implemented cool features, and studied various game mechanics. We've considered how to do things properly to respect genre standards and meet player expectations, and you've learned some useful game design principles focused on fun and entertainment. But those were genre-specific concepts. So, how can we make all our games fun, regardless of genre? What questions should we ask ourselves? What are the best paths to follow for good game design?