Seriously, this show is the best thing to happen to anime. No? Well, to start with cons, the plans for R2 were abruptly changed, and you can feel that throughout the season. The subtle hints and setups in R1 are covered only in extra material, but this doesn't take away from the anime as a whole, because face it- there's pleeenty of plot to cover in only 25 episodes. This makes things seem rushed, if anything.
The thing about Code Geass is it is super-ambitious and super-compact— it has a goal and it's heading there full speed and with no regard to your feelings, which WILL get stomped upon as you watch Lelouch and Suzaku hash it out on everything from full on mecha battles to friendly school buddies. Completely seriously. And despite your best efforts, you will be sucked in and sobbing by the end.
Thus is Code Geass- the most glorious ideological battle known to anime. When I see Lelouch compared to Light, the only similarity I see is their willingness to kill. The emotional side is handled completely differently. He's a great character- cool and genius and ruthless, except when he's not, in which case he is less awesome and more heart-breaking. Another great, great, great factor CG throws in your face is his 'best friend' Suzaku, which is your more typical innocent, righteous, athletic, earnest hero-type EXCEPT WHEN HE SUDDENLY ISN'T in which case he will be heart-breaking in a different way. Their interactions and pasts and beliefs are set against eachother from the get-go, and both sides are evil and just depending on the way you tilt your head. Talking about it would take pages, so just use your imagination, which Code Geass can supply in spades. Something I read mentioned 'sublime deaths'- which is true, people can be killed by the millions or one by one and when CG deigns to focus on a character, you will feel things stabbing your heart as they smile their last smiles. Conclusion: Code Geass has amazing characterization/interaction.
Let's talk plot. Plot is...a definitive factor. It redefines the word: 'plot-twist' and occasionally 'duex angst machina.' You can only hate it because you are so invested in Lelouch's crusade that if it's put wrong, you cannot handle it. It's believable and strings you along forever. The payoff at the end is like a huge release of energy and you will NEVER forget it.