Crush graham crackers into fine crumbs. Mix with granulated sugar in a medium bowl until evenly combined.
Pour melted butter over the crumb mixture and stir with a fork until all crumbs are moistened and the mixture resembles wet sand.
Press the mixture firmly into the bottom and up the sides of a 9-inch pie pan, using the bottom of a measuring cup to pack it tightly. Chill in the refrigerator while preparing the filling.
Place softened cream cheese in a large mixing bowl. Add ½ cup powdered sugar and beat with an electric mixer on medium speed for 2-3 minutes until completely smooth, light, and fluffy with no lumps.
Pour in eggnog, vanilla extract, ground nutmeg, and ground cinnamon. Beat on low speed first to avoid splattering, then increase to medium speed and mix for about 1 minute until well combined.
In a separate medium bowl, combine 1 cup heavy whipping cream and 2 tablespoons powdered sugar. Beat with clean beaters on medium-high speed until stiff peaks form. Be careful not to overbeat.
Add about one-third of the whipped cream to the eggnog mixture and gently fold in with a rubber spatula. Add the remaining whipped cream and continue folding gently until no white streaks remain.
Pour the filling into the prepared graham cracker crust. Use a spatula to spread it evenly and smooth the top. Cover loosely with plastic wrap and refrigerate for at least 4 hours, preferably overnight.
About 30 minutes before serving, combine 1 cup heavy whipping cream and 2 tablespoons powdered sugar in a clean bowl. Beat until stiff peaks form. Spread or pipe over the chilled pie and dust with ground nutmeg.
Remove the pie from the refrigerator about 10 minutes before serving. Cut clean slices by wiping your knife with a damp cloth between each cut. Serve immediately.