I agree with natsume and Glath about KYNK. It's one of my favorite Ringo singles, right up there with Honnou, Mayonaka wa Junketsu and Ringo no Uta (due in no small part to the single version of Sakuran, which I prefer to the album version).
I dump all over HF on a semi-regular basis, but the truth is I actually don't really mind it (the new cool, or probably the cool that has always been, is to talk about how much something sucks and how awesome you are for recognizing and rejecting that uncoolness). I've always had a tingle in my nethers for songs like Gamble, Stem, Ishiki, Yokushitsu, Meisai and Yume no Ato, and these new versions really do it for me. But since this isn't about new versions of old songs, I'll say that Hatsukoi Shoujo, Oiran, the album and Death Jazz versions of Karisome Otome and Sakuran (possibly both versions, definitely the single version) rank pretty high up there on the Ringo Ranking for me.
I love Education and Adult more than MM and UM, as much as SS and less than KZK; needless to say, they're ranked high, so of course I'd be inclined to think that they can hold their own against Ringo's solo material. I agree completely with Maou about the Sounan single. Kokoro is probably my favorite Ringo song out of both solo and Tokyo Jihen material.
Variety, for the most part, I don't like (despite enjoying the OSCA/Killer Tune singles and Senkou Shoujo). I think Ringo needs to stick to the songwriting, because she's written some phenomenal shit in the past. Kameda can stick around, too, because he ain't half bad.