1. Johto
GOOD:
1. ALMOST every one of Ash's Pokemon battled.
2. Pikachu didn't hog.
3. The teams Ash used were interesting (i.e not Pikachu, 3 starters, 2 randoms that get no wins).
BAD:
1.Kingler was maltreated for no reason.
2. Kanto starters hogged a little too much.
2. Sinnoh
GOOD
1. A fair amount of reserve battles/Sinnoh team battles.
2. A good amount of battles. (no only 2 non 1vs 1 battles)
3. Fantastic tactics and strategies contributed to it being the most unique league.
BAD
1. Tobias.
2. Certain Pokemon were given too much focus e.g Pikachu, Gible, Heracross and others e.g. Muk, Bayleef, Kingler etc. got nothing.
3. Skipping battles as though they had no time, after one of the longest and most drawn out saga's in history!
3. Hoenn
GOOD
1. Loads of battles, inckluding multiple 6 on 6's.
2. Interesting battles and league opponents.
BAD
1. NO reserves which made for Ash having the same 6 every battle, very boring in that respect.
2. Torkoal was shafted for no reason, there was no excuse given it was in only 6 Pokemon were used.
4. Kanto
GOOD
1. The battles were enjoyable, particularly Kingler and Muk's.
BAD
1. No 6 on 6's.
2. Charizard sleeping was PATHETIC of the writers.
3. No battles for Pidgeotto was unfair.
5. UNOVA
GOOD
1.Stephan's battle, bar Leavanny being screwed over.
BAD
1. No reserves.
2. NO genuine 6 on 6, one 5 vs 6 (!), one 1 vs 1 and one 3 vs 3.
3. Main Rival battle was a 1 vs 1, with a DEM Pikachu win.
4. Skipping battles for no reason and instead showing a stupid Filler.
5. TERRIBLE apportioning of wins, with Pikachu and Pignite hogging YET AGAIN as they had done in the gyms, and Krook getting an unfair extra win. Had they shown Ash lost to Cameron's 6th rather than 5th, and including Scraggy's win, there were 10 battles, meaning each Pokemon could have got one win each. Instead the favorites stole the spotlight.
6. Ash losing to a moron.
In short Unova was by MILES the worst league in my opinion. At least I enjoyed the Indigo league even if it was bad.