I finally finished re-watching the series, and had a ton of fun reading through this AWESOME Wiki while doing so! I know for a fact I'm going to try and convince and many people as I can to get into the show, and at the very least watch the full second season which I believe is Code Lyoko at its best and most complete!
Watching the original show and Evolution back-to-back made me realize just how much effort was put into the original; designing the characters so that they truly look, move, and emote the same way both on Earth and on Lyoko, TRULY making them feel like the same person the entire time! This, combined with the heightened sense of realism in the life-or-death action scenes, makes the show have a sense of urgency and excitement unlike any other! The drama may be messy and non-conclusive but that only makes them feel like real preteens even more!
My favorite episodes are Common Interest for its one-of-a-kind premise, A Bad Turn for the BEST action scene in the show bar none, The Key for its emotion and sense of conclusion, and Echoes for the way it finally forces the characters to mature once they're out of their years-long comfort zone! I also think the first book, The Underground Castle, is an excellent retelling of the original story, and provides a far stronger emotional core than the episodes it is based on.
See you later, Code Lyoko! I can't wait to come back in a couple of years and relive it all over again.