I would say
XY Ash > DP Ash > Battle Frontier Ash > Hoenn Ash > Johto Ash > Kanto Ash > Best Wishes Ash
Kanto Ash = Noob (Justifiable since he was just starting)
Orange Islands Ash = Still Noobish (He didn't really HAVE to battle a whole lot during this time. 4 "Gym Battles" and only 2 of said "Gym Leaders" he had to battle excluding their actual leader).
Johto Ash = He's improved enough to where he doesn't need Brock or Misty holding his hand anymore, he's more strategic. A notch above noob level
Hoenn Ash = He's decent, he's good enough to take May on as his Kohai.
Battle Frontier Ash = He's good a mix of how he was in Hoenn and how he would be in DP.
Diamond and Pearl Ash = He's really good, came up with good strategies, he's mature, and MUCH more competent than he was in the past. It took a guy with a team of Legendaries to stop him.
Best Wishes Ash = Noob AGAIN (No excuse for why he was this stupid. He was so dumb he FORGOT his Snivy was a girl, was at a disadvantage against an Emolga, how to properly catch a Pokémon, and only brought ONE Pokémon barring Pikachu to a Gym Battle and had to LEAVE said gym battle to get another Pokémon and to top it all off he lost in the Unova League to a guy who an even BIGGER idiot than he was...even PIKACHU was agitated with his stupidity in Best Wishes).
XY Ash = He's great, all of the maturity, experience, and competence he's gotten as a trainer is back. He came up with good strategies with training or on the spot. He had probably his best regional team of Pokémon yet and a powerhouse with Greninja. It took an OP as all Hell Charizard and PIS to bring him down in the Kalos League. In general XY Ash is smarter than he was in the past with only his obliviousness being what makes him look sorta dumb.