Reasons that show Ash is a bad trainer :
1. He NEVER EVER evolves his Pokemons, and has only a handful of Fully-Evolved ones ( Charizard, Sceptile, Snorlax, Gliscor etc.) He only uses weaklings that are babies and thats why he always loses.
2. He has a bad habit of letting his Pokemon stay with Prof Oak or have them fully released for stupid reasons, most notably, for the purpose of catching new Pokemons. I think this idea is stupid. :S
3. What else? Oh right! How can I forget his DUMB DUMB LUCK??? He has never EVER won a battle without the involvement of his sheer luck. And LUCK, is something a trainer must never depend on fully.
Reasons that show Ash is a good trainer:
1. .... Ash is a good trainer??? LMAOFFFF !!!
But blah!
Who cares about Ash being a good trainer or a bad trainer anyways? Pokemon, and other popular animes, have been made strictly from people's imaginations, and doesnt concern real life at all.
Well, I may be wrong though, it does affect real life, but in a totally different way than we think.
" Its all about the M-O-N-E-Y!!! "
Heck yah, it's all about the money alright, cause the only reason Ash is a " bad trainer" and never evolves his Pokemon or stuffs like that is ONLY FOR THE SAKE OF NINTENDO'S PROFIT.
Just like many people said here, if Ash really had a team full of Fully-Evolved and Highly Trained Pokemons, then he would have been unstoppable, and leading to 1HKOs in any battles he faces, which would make the anime BORING and less attractive TO YOUNG CHILDREN WHO ADORES CUTE LITTLE POKEMONS.
So, Ash being a good trainer + Having a Powerful Team - Children's Attaction to Pokemon = Nintendo's LOSSS
So thats it. That's my point of view. Hope you all share my opinion.
Have a good day!