I liked K'9999, but they had to call it quits after a couple of games. Using him twice was an homage... making him a regular character would be a full-blown Akira ripoff.
Screw Vanessa! All she's ever been is a poor ripoff substitute for Rick Strowd. If you want some Rick Strowd-ness in your KOF, why not use Rick Strowd???
Lin was decent, but Duo Long is better. Pity they couldn't balance him. I wouldn't mind seeing Eiji again myself, that character had flow.
Let's see... Angel was to anti-intuitive, Foxy had potential but too much priority on the DP, Heidern has always been overpowered, and Andy was getting repetitive over the last few KOFs.
The only character mentioned above that I can really say I miss is Ramon. They finally unlocked his potential, but didn't bring him back because he'd have had those deadbeats Seth and Vanessa with him. He needs to join another team somehow.