I just decided to pull a few predictions. The teams are, obviously, assumptions on my part.
Ash:
Heracross (Super-effective moves to counter Darkrai, in addition to flight which could help. Not sure how.)
Pikachu (Pikachu is usually used in the last battle of a region.)
Totodile (Hasn't battled)
Bayleef (See Above)
Glalie (Can play a fall-guy.)
Quilava (Didn't showcase two of its new moves, got a horribly rushed battle, and it'd be odd having two starters without the third.)
Takuto:
Darkrai
Cloyster
Houndoom
Cacturne
Lucario
Isshu Pokemon/Pseudo Legendary
Match Predictions:
Darkrai -VS- Quilava
Ash opens with his newly evolved Pokemon and orders an Eruption, kicking his Offense into overdrive, not wanting to be overwhelmed by the Legendary. Darkrai easily dodges and puts Quilava to sleep. Ash switches him out.
Darkrai -VS- Bayleef
(Bayleef was a major hitter in the Johto League so it can risk the loss.) Darkrai attempts to put Bayleef to sleep but Ash is able to counter just in time. Bayleef battles valiantly but falls immediately after dealing damage to Darkrai.
Darkrai -VS- Glalie
Glalie takes a major beating, hardly dealing damage at all before fainting. (Glalie won all three of his League matches before so he can handle the loss.)
Darkrai -VS- Heracross
Heracross is able to avoid getting put to sleep by flying out of range. His attacks deal major damage to Darkrai, so Takuto pulls him for another Pokemon.
Cacturne -VS- Heracross
Heracross takes out Cacturne fairly easily without taking a single hit.
Houndoom -VS- Heracross
Ash immediately recalls Heracross once Takuto sends out Houndoom.
Houndoom -VS- Totodile
Totodile pulls off an unbelievable victory that goes down in the record books. Or just beats Houndoom regularly. Your choice.
Cloyster -VS- Totodile
A water-Pokemon bout goes on for awhile, but Cloyster seems to have the advantage. Ash decides to recall Totodile after taking major damage.
Cloyster -VS- Pikachu
Pikachu has no trouble defeating the Cloyster that had taken damage from Totodile and Ash immediately recalls.
-Intermission-
Quilava -VS- Lucario
Quilava takes an Aura Sphere but awakens immediately. The two Pokemon have a long showdown, Lucario taking the advantage. A finishing blow is launched from both Pokemon and Lucario is stays up longer than Quilava, giving Takuto another win, leaving both trainers with three Pokemon.
Totodile -VS- Lucario
(Who wouldn't wanna see Totodile take out a Lucario?) After being severely damaged by Quilava, Lucario is taken down easily by Totodile.
Totodile -VS- Darkrai
Totodile doesn't last very long against the Legendary and is defeated without landing a single hit.
Pikachu -VS- Darkrai
Pikachu doesn't seem to be dealing any damage to Darkrai but is able to avoid being put to sleep by using his speed. Ash recalls him.
Heracross -VS- Darkrai
Heracross prevails in the end, taking down what was thought to be Takuto's strongest.
Heracross -VS- Fifth Gen Pkmn./PseudoLegend
Ash didn't count on Takuto's mystery Pokemon to be stronger than Darkrai as it is able to take Heracross out with ease.
Pikachu -VS- 5Th Gen Pkmn./PseudoLegend
Pikachu fights a brave battle but falls to the strong Pokemon, League closes and Ash and everyone go their seperate ways.
So that gives:
Quilava: No wins, two match-ups.
Bayleef: No wins, one match-up.
Glalie: No wins, one match-up.
Heracross: Two wins, Four match-ups. (Five if you choose to count Houndoom.)
Totodile: Two wins, Four match-ups.
Pikachu: One win, Three match-ups.