Well...I can't pick between these two, I liked them equally for different reasons:

ARIA the Orgination
Itazura na Kiss

Aria was the first anime title to actually, truly shock me. With a plot twist in a slice of life series no less! Especially one typically known for a lack of developments. Racing heartbeat, stunned expression, the works. I found it shocking enough that I couldn't get to sleep for two hours after. For a series I usually used to unwind and relax right before bed, this was no small feat. That alone blew me away, but the series still carried an awesome air of peace, and finished it all off with an excellent time jump conclusion. There's a lot more to this series' final 5 episodes if you listen carefully into the dialogue.

Itazura na Kiss on the other hand, was a really excellent romantic comedy. A series that goes beyond high school and even into married life (gasp!). Nana Mizuki playing the lead Kotoko however, sold the series completely. She mixed a perfect balance of emotion during serious parts, and humor during the rest. I doubt any other actress could have played the role as well as she did. Funny, touching, endearing.


Runners up (no order):

Kannagi
Macross Frontier
Kyouran Kazkoku Nikki
Ga-Rei Zero
Bamboo Blade
Real Drive

Macross Frontier fulfilled my needs for action. I've always been a fan of Macross series over other mecha, it's probably entirely because the VF-class planes. I liked the music more than most other series, I'm still listening to Diamond Crevasse and Northern Cross (the two EDs) months later, and it's really hard to beat a Yoko Kanno soundtrack. I found myself looking forward to this series the most too. While Code Geass was the MUST SEE Sunday series, the beginning and middle of R2 was so weak and poorly written that the entire series soured for me. That keeps it off my list. A pathetic season with a kickass ending doesn't make up for shortcomings. There were far too many questions unanswered, and the episodes before the finale were filled with way too many decoy ships, horrible plot holes, and too-abrupt "twists" we all saw coming. Sure, Macross F has a non-commital ending (but we all know he totally picks Sheryl ),