episode of nami is probably the best. i'd say in some ways it can even be on-par (or maybe better to u) with the tv-series version. the special doesn't jst drop you in the middle of nowhere either (like episode of alabasta did) so that feels like a complete story. epic moments still feel epic (even-tho it's been some-time since i watched i can't rly remember everything. i jst remember liking the tv-special a-lot.)
episode of east-blue is also gr9. despite adapting nearly 100 chapters worth of story into 2 hours iirc. i liked the ending a-lot too with the new version of "we are". truly felt like that was for the 20th anniversary to me.
episode of merry, i saw some of (like the beginning but i can't rly comment i think). same for episode of sky-island.
episode of alabasta sucked, i think. hd can't rly help it either. comparing luffy defeating crocodile in the original tv-series to the movie is not even close. not only that but there's no context & some are also censored iirc, like crocodile impaling luffy in the 1st fight.
episode of chopper, i also can't say much abt sadly, i don't think.