Best - TPM Naboo Fighter. I bought the Playskool version when it came out and even now I will take it for a spin around my apartment making *vooosh* sounds.
Runner-up Best: Dooku (from ROTS). I'm a Dooku collector and this is one of my favorite pieces. it captures his regal bearing and scowl as well as trademark curved saber hilt.
Worst - Rancor. It bears no resemblance to the Rancor in the movie and doesn't come close to being the right scale. If you don't have the budget to make a giant monster, then don't make a giant monster!
Runner up Worst: Obi-Wan's Jedi Starfighter. The cockpit is so big you can fit half of your GH collection in there with him!