There were many so far main group who gave company to Ash as they began to better understand themselves and work on creating meaningful friendships. And AG, DP, BW, XY cast all having their flaws, endearing traits and positive sides to it.
But original trio wins first place for me.
Ash,
Misty and
Brock were group which started everything, introduced to us world of pokemon and to this day i can't but not to like their friendship and close bond they build around themselves. They had perfect level of understanding between themselves, lot of moral support and lot of flare, humor and dynamic interactions between themselves with no one feeling left out staying consistently fun for pretty much whole original series period.
Ash naivety and stubborn attitude not wanting to listen to his friends and do things on his own getting into clash., Misty flamboyant, sarcastic nature coming up with various jokes and taunts, while showing herself to be sensible pulling out from Ash his best through bickering, fierce rivalry and showing of they had between themselves packed with Brock who was absolutely hilarious and vibrant as character being supposedly most wise and intelligent group member while having himself issues to deal with finer things in life looking for consolidation among his friends when getting into trouble with girls etc. producing natural, unforced and enjoyable dynamic between characters.
They captured perfectly message of pokemon being about friends which are there for each other, help themselves to move forward or give backbone on which you can rely when feeling down joking with each other, having fun laughing, talking about their dreams and issues comforting themselves and giving motivation not to give up while arguing or being annoyed at each other flaws sometimes just like real friends would do.
I liked how their friendship was strengthened even more over time from Kanto end of Johto developing very strong bond between themselves, and giving out impression of companions which passed through many things knowing themselves for long time with interactions containing lot of comedy, sarcasm and emotion.
And their departure perfectly encompassed on that when Misty was about to break down in tears clearly growing to love Brock and especially Ash not wanting to leave, while Ash was completely heartbroken not being able to suppress bursting stream of emotions running on surface being appreciative and grateful for everything those two did for him. With this three coming long way building on incredibly close bond and care between themselves. More than any other group Ash traveled with did in my opinion.
For DP they should have axed Brock and had Barry be the male companion so he could have some chemistry with Dawn. The DP trio should have been Ash/Dawn/Barry and it would have had some great chemistry...instead the writers made the mistake of bringing Brock back and soured it all.
Because "problem was clearly in Brock presence", rather than writers themselves putting too much attention on Ash and Dawn promoting their friendship as 2 co stars who were followed through DP?While leaving not just Brock, but big chunk of rivals and recurring characters in dust.
Whoever was put in Brock place would be treated same unless whole repartition of focus and ideas writing staff followed when writing Sinnoh saga wouldn't be changed.
