What makes Goldfinger the best Bond movie? Probably it's the most thrilling entry with memorable characters, gadgets, and scenes.
Gert Frobe (dubbed by another actor because he could barely speak English) is great as Auric, gentlemanly geniality barely concealing menace. Harold Sakata is also really good as Oddjob, Goldfinger's hat-slinging mute Korean manservant.
Honor Blackman is a fine Pussy. Shirley Eaton is good fun as Jill. Tania Mallet is not quite as good, as Jill's vengeful sister Tilly, but does OK.
Guy Hamilton's first (and easily best) effort as director set the standard for the series for many years to come, introducing an overall jokier tone than the previous two, most obviously in Bond's affectionate needling of the grouchy Q.
The score is one of John Barry's best (for me, it's second only to OHMSS), and the Shirley Bassey theme song has rightfully become a classic.
Overall, this is still probably the best Bond movie ever made.