This review may contain Spoilers
Note: This will be a review of the entire main storyline of Code Geass(R1 + R2).
For newer anime fans, one of the most frequent recommendations they get is often Code Geass and for good reason, its a common stereotype that "animation is for kids" and therefore a poltical warfare-based show shows that this stereotype is wrong. So how good is it?
Visuals
The art is weird at first, the proportions are overly skinny and thin but you get used to it after a while, and some of the Mecha designs are just plain cool despite not being as much of a selling point like other contemporary Mecha shows like Gundam. Not breathtaking but overall, it's pretty good.
The animation is also good, you can have a few action scenes that are just a really fun watch however you probably won't be getting any Ufotable-level sakuga from this show.
The directing is not too special but gets the job done.
The visuals overall are probably not one of the best out there but they're great nonetheless

Characters
If we dissect each character of the show, you'll find that not all of them are great... I'm talking about you Nina. In all seriousness the main criticism I have with the characters is that they can often be inconsistent, they do very uncharacteristic things a lot of the time however they are certainly not bad I would say, especially the protagonist himself; Lelouch who in my opinion is one of the most well written and compelling protagonists of all time and the antagonists do their job but dont really elevate the show to a higher degree like some other villains do. Overall, a good cast but with minor problems ehem...Nina.

Plot
The basic plot is essentially Lelouch using the "power of absolute obedience" to lead a rebellion against the Britannian empire with the mission of bettering the world. It is a political thriller and a mecha show, yes, but doesn't use the latter as its primary focus which is generally a good thing. The plot is given more space to become more complex and less like your generic mecha show where they fight monsters every week, following Lelouch as he leads a rebellion against Brittania alongside his Black Knights. Although, the problem is that the story can be up and down, and throughout the entire show, this imbalance can be very obvious. The plot can swing hard from a well-thought out, strategic, and political drama; and some episodes dedicated to making a giant pizza or chasing a cat. However when the show is focused on its core conflict and less on pandering to the audience, it can truly be great, though at times, the writing leans too heavily on plot conveniences which can hurt the overall product. But of course a review of code Geass wouldn't be complete without even a mention of its ending, It is what might be the greatest ending in all of fiction, of which I cannot get into without getting into major spoiler territory so you'll have to watch the show yourself to experience the masterclass of Code Geass' ending. When people say it's good, they aren't exaggerating and despite a few problems I have with the show, it was definitely worth to watch it just for the ending as it concludes most of the plot threads that the show presents in a meaningful way and delivers on every ounce of its themes about true sacrifice and peace. It is not a perfect story by any means and can be messy at certain points but overall, despite a few issues here and there, it is still certainly worth your investment if you can stomach a few plot conveniences and occasional iffy writing.

Sound and Music
The Voice Acting is great for both dub and the original especially in the part of Lelouch, it's solid.
Sound Design is good but not especially memorable.
It has a bunch of banger Opening themes especially the first one, The Ending themes are similarly very good and the OST is great and at times amazing, not much too say except that the music is for this show is good.

Other Stuff
The Geass system is a very interesting concept, it provides a strategy-based system rather than the often problematic "power level" system that a lot of shonen have and so it makes for much more interesting battles
There is a lot of fanservice... like A LOT, not necessarily a bad thing though

As flawed and inconsistent as it may be, you cannot discredit the ending to the show, it is the culmination of everything after all. As a certain monk once said "Code Geass is a car crash that somehow perfectly parallel parked" and that definitely is the case here. Perfect? No, far from it in fact, but is it a must watch? Absolutely.