I'd probably rank it from highest to lowest; May, Dawn, Misty, Iris.
Not that the order is from best to worst, just that May added some sideplot as a reason for some filler to exist, whereas Misty didn't really do much...even with the Pokemon that COULD battle on Land (even then, Horsea/Goldeen are seldom seen) which just left...Psyduck, Poliwag/Toed and Star(yu)mie....her potential just got shifted to the person to yank Brock's chain back whenever a girl is near.
Dawn in some respects could be seen as an inferior May whereas May only had Harley and Drew as rivals, Dawn had Zoey and Ursula (for a few eps) though the contest episodes in D/P just had more coordinators that was more genuinely interesting than Dawn (as a character) herself.
May coming back was just awesome, wouldn't be surprised if her Wallace Cup outfit got her a lot of fans...
Seemed strange that they had the need to introduce some sense of nostalgia prior to N though, Cynthia made sense but Iris having a battle with Dawn was.....weird, she had no reason for follow Cynthia to Unova unless the directors were fond of shipping....guessing Dawn won because she had more evolved Pokemon right...?
>>12009662They're pretty nice gloves, also those bike shorts and that Bandana...
>>12010039Technically that May is Sapphire from Adventure/Special...think she's supposed to be slightly feral-looking due to her back story.