What made it good ?
Shinji is the best rival ever made still to this day. His transition from being pure hatred to having his story explained and his "redemption" put by Brendan that Satoshi beat before.
Goukazaru's story and evolutions, being the link between the two trainer (remember Sinnoh legends? When two people meet, something is born)
Plant starter has a little story with Shinji too.
Concours are an evolution from Hoenn's one.
Satoshi's meet with all the member of the elite 4 in a single generation and have a match with two of them "training" him.
He meet Shirona (Cynthia) the regional master and became friend with her and do multiples aventures in a dozen episodes.
Satoshi has a good team and he even decided to use his old pokémon in the ligue putting him with a really good team if he wanted.
4 seasons were made and like the AG arc, it could mean that everything was made for Satoshi to either :
What was really bad ?
Legendary pokémon being used by Tokuto (Tobias) and Nurse joy in the special.
What is good ?
The Team Rocket : The (black uniform) TR is active and got some "serious" plan and acting on multiple épisodes.
Animation : Being a continuation of the quality & techniques, animation is better than the previous generations even though I think some things may be a little too much due to CGI.
The opening/ending song: I'm only talking about the song here since I'm not fan of the full 3D animation of the first opening of B&W.
Rivals are seen many times on multiple events : I found that really nice to see them on many tournements and not just insulting each other and having simple battling and even if most chars are globally annoying, it is a normal child behavior (don't forget most should be 10-11)
What is really not good?
Shooti is a really low quality Shinji (Paul).
Ash and Pikachu being reboot even though Pikachu still have his Volteka which is a high level technique.
Dento, what the fuck with pokémon sommelier. It would have been better being in XY since it's based on France.
Iris is fucking annoying and give nothing to the story to the contrary of Haruka (May) & Hikari (Dawn)