Ah, 'Code Geass', always a crowd-pleaser. You know, sometimes, the order in which you watch a series can directly affect your understanding and enjoyment of the story, and this is definitely the case here. For 'Code Geass', there's a generally accepted watching order that fans have agreed on, which will optimize your binge-watching experience. Here goes.
You'll want to start off with 'Code Geass: Lelouch of the Rebellion', which is the first season of the show. This season sets up the world and introduces you to the characters, especially Lelouch, our antihero protagonist. It's got 25 episodes, each jam-packed with political intrigue, mecha battles, and Lelouch's complex schemes.
Next, move on to 'Code Geass: Lelouch of the Rebellion R2'. This is the direct sequel to the first season, and it runs for another 25 episodes. R2 continues where the first season left off and escalates the conflicts presented in season one. It's a thrilling ride towards the end of Lelouch's journey!
Now, for a slight detour - you can watch 'Code Geass: Akito The Exiled' a five-part OVA series. This isn't directly linked to Lelouch's story, as it takes place between the two seasons and focuses on a new set of characters. Still, it's a pretty cool side story, and it offers a fresh perspective on the Code Geass world.
Lastly, we have the latest entry, 'Code Geass: Lelouch of the Resurrection'. It's a full-length film that continues the story after the events of R2, and it provides a conclusion (of sorts) to Lelouch's story. But no spoilers here, you'll have to watch it to find out what happens.
And that's it! If you stick this order, you should be able to get the most out of 'Code Geass'. And remember, in the world of 'Code Geass', expect the unexpected!