I like games that give me tools and let me decide how to use them. Games with emergent, interconnected systems that reward exploration and experimentation. Games that blend the static and scripted with the systemic and emergent such that the world feels reactive and alive with possibilities. Games where everything you do is a choice.
Deux Ex games take these mechanics and intertwine them with narratives of espionage and global conspiracy, filled with major and minor characters with diverse motivations, goals and loyalties, and leave you free to find your own place and role in their world.
Mankind Divided is the most successful game at doing all of that since the original Deus Ex.