I personally like every Ringo period, from the relatively simple alternative rock on Muzai Moratorium through the more complex alternative rock on Shouso Strip all the way to the completely schizophrenic avant-garde Karuki Zamen Kuri No Hana.
The 'creepy blue eyes', I take it that's Mayonaka Wa Junketsu? I must say I don't think that's a very good example of Ringo-chan's musical evolution that eventually resulted in Karuki Zamen Kuri No Hana. It's excellent, but quite standard, only different from earlier material because of the collaboration with Tokyo Ska Paradise Orchestra. The alternate version of Sid To Hakuchuumu showed once more Ringo's love for old big band and jazz, but it didn't really prepare anyone for Karuki Zamen Kuri No Hana, I think. Aisako No Chousoku was flat-out brilliant by the way, one of my favorite b-sides, but once again, quite standard in comparison to later work.
If I had to choose, I'd go with her KZK-period. Ringo really outdid herself then. KZK is a masterpiece (in my top 100 of all time it ranks at #4) that will never cease to amaze its listeners. Of course, I couldn't live without her older albums either, and I must add that I think that some of Ringo's b-sides are some of her best songs/covers (Aisako No Chousoku, Tokiga Boosoosuru, Can't Take My Eyes Off Of You). So eh, hard to choose, haha.
Meisai isn't on the Ringo No Uta single by the way, but on Kuki (STEM) ~daimyo asobi hen~, and on KZK of course. I'm not sure if you knew that, your post confused me there, haha.
