I'm not an expert on animes, but I know an amazing ending when I see one. Code Geass Season 1 surprised me with its feeble finish and I knew I had to see R2. When I look back on Season 1, I realize that its ending built the perfect pathway onto R2.
I'll make this short because words cannot really describe how good the series was.
Story: If you watch it till the very end, you will be amazed. This story does NOT disappoint.
Art: Simply gorgeous. Beautiful sharpness of the lines in the face, just the right amount of sparkle in the eyes, and tear-jerking expressions.
Sound: Liked it enough, I don't worry too much about this.
Character: Generally very well-developed characters, even in people who are not very important. There's a side-story for almost every individual and whether or not you adore the main plot or the sub ones, R2 will keep you on edge.
Enjoyment: I've watched it twice, and I've cried both times. Mind you, these tears explain not the sadness of the series, but rather the magnificence in its quintessence. I cannot stress enough how complete this series was compared to many other series.
Overall: I've got nothing bad to say. I loved every little bit down to the subtle complex love relationships going on. And although I know it'll never happen, I will always forever be waiting for R3.
10/10