10. Kerbal Space Program
Y'know all those people that end any discussion on a faux-complex topic with, "It's not rocket science"?
Well, Kerbal Space Program IS rocket science, and it's absolutely phenomenal.
An unabashedly complex, unforgiving toolbox of ship components, physics interactions and rocket propellant, you're tasked with everything from achieving space flight to maintaining velocity, landing on a number of planets to even just not imploding in mid-air. On consoles even the menu interface is more daunting than a Dark Souls boss, and that's before you get to all the real-world inspired "quirks" that come with mastering space travel.
If you're going to conquer the stars, Kerbal REALLY wants you to earn it. Do you have what it takes?