Ash's Strongest Team | Bulbagarden

I love how you put the aces in the first spot on the regions, but here is the thing: Neither Lucario, Glalie or Greninja are the aces in their respective regions.
Lucario is weak compared to Sirfetch'd, Dragonite and Dracovish in base form and really needs its Mega to shine against stronger opponents (Unlike the three i mentioned, they don't need a power-up to defeat a Elite 4 mon/Mega or champion mon).
From a storytelling perspective, Greninja might seem to be the ace, but from an impact on the region battle wise, Greninja isn't the ace... impact wise, Talonflame is the ace... since it never lost a battle in the league without taking another mon with it, it fought in the most gym battles, only skipping one gym (Clemont) and not losing in any gym without taking another mon with it (Except against Grant).
Hoenn basically had 2 aces... the overall ace Grovyle and the league ace Glalie, but i still think Grovyle is supposed to be main ace.

Based on the Masters Eight and before
1. Sirfetch'd
2. Dragonite
3. Dracovish
4. Lucario (Without Mega)
5. Gengar.