I didn't say PapaKiki's plot was bad, I said its direction was bad. Maybe I should rewatch it, but I do remember thinking the flow of the story felt a bit off. Characters weren't exactly likable either, usually I like tsunderes but Sora was annoying as hell and Yuuta was a limp noodle. I did like the character designs, but as we all know from Mashiroiro Symphony, character designs alone can't save you.
K-On and other KyoAni stuff like Hyouka and Tamako Market are kind of boring, true. But for whatever reason, I actually like that "boredom" that these series have - maybe it's because they're so peaceful and "normal" and it gives me a break from the war-torn Universal Century.
Code Geass is far from perfect. R1 was great, almost amazing, but R2 was fucking awful. I can go and list everything I hate about R2 but that can wait. Except for the ending, which was good.
I consider the first Gundam series and Zeta Gundam to be one experience, one should watch both to fully appreciate them because of the Char/Amuro thing. Definitely two of Tomino's best works. And yeah, SDF Macross is amazing. It's much more lighthearted than Gundam if that's your thing.