In video games, as well as other mediums, "immersion" is the zen-like removal of the game interface, where thought and action are one. Once a player can become immersed, they can achieve "flow," which is the ultimate state of consciousness you can achieve in gaming.
When you can forget about the interface, as in playing music on a mastered instrument, you become the instrument. The same holds true for gaming.
The measure of the game designer's skill at creating immersion is therefore the amount of time it takes to get past the interface. Creating a slick experience that trains the player to be an expert by using the interface, rather than requiring them to read a manual is fundamental to this experience.
By beginning with the core controls, and adding more over time, ideally by letting a player experience them rather than lecture them, game designers / developers are able to convey a sense of exploration and learning that bond players with the experience in a profound way.
Super Mario is a fundamentally beautiful experience, simply because you are "forced" to learn and master the base mechanics immediately and entertainingly. A thing of beauty upon your first try. I can remember it well.
The best games create these learning experiences in memorable ways, hopefully having a degree of leniency as well as challenge.
Teach your players to be masters secretly. They need to master their environments and the game's controls to become fully immersed, and your role in this experience is to be an invisible teacher. Are you up to the challenge?
These are my thoughts. Love to hear yours!