Twilight Imperium

You lead an alien civilization to galactic dominance. You expand your fleet, trade with neighbors, and engage in political voting. The sheer scale is massive and involves a lot of table talk. You can conquer planets by force or secure objectives through diplomacy. It takes a solid eight hours to finish a standard session. You need a dedicated group who is willing to commit the entire day. It is an epic event rather than just a casual game. Bring plenty of snacks.