OK I think its goes like this (In My Opinion) From strongest to weakest Im not including ash's sinnoh pokemon since that hasn't ended yet and its not fair to add them in since they haven't had as much experience as the others, but I am going to include those he has released/given up. Charizard, Sceptile, Snorlax, Glalie, Pikachu, Donphan, Pigeot, Bulbasaur, Squirtle, Swellow, Heracross, Bayleaf, Tauros(the one he uses), Corphish, Torkoal, Muk, Lapras, Primeape, Kingler, Totodile, Cyndaquil, Kingler, Nocktowl, Butterfree. Thats just my idea I kinda think charizard is only the strongest because he trains with all the other charizards at the charicific valley, sceptile only has ash's other pokemon to battle and the best one for it to battle is snorlax so thats what I think.