hmmm its hard to decide which one is most intelligent...... coz each everyone of them got different factors to decide which is intelligent....except for luffy,zorro,sanji & brooke
... brooke & sanji are just average to me... and luffy is just dumb... and zorro is almost average..but he got that no sense of direction
for example of those factors
robin archeologist... got a decree of doctorite in archeologist at age of 8.... hmm a pretty genuis..
chopper born on island which the best doctors are produce....and being a doctor is not that easy...
ussopp... to think ...to make those gadgets...and to come up (funny)tactics to beat his opponents
franky.... to make those boats since at his young age...and his body being a cyborg... his engineering skills... is not just typical
nami... being a Cartographer ..to draw those map very acurately...doing land survey and stuff.. is hard to do that..
so its hard to rate which one is intelligent...and also in fights...