Kinda hard to say for all pokemon have their strengths and weaknesses (except Torterra and Torkoal ) but this how I would rate them as of now.
Pikachu: This thing has defeated many powerful pokemon like Dragonite, Regice, and recently Latios. Ash just needs to use Volt Tackle less so its not sucj a kame-kaze.
Skeptile: Defeated Darkrai so major props for that and was able to tie with a Blaziken when it clearly had a disadvantage.
Charizard: Defeated Articuno and fought well against an entei with hax crystals.
Infernape: Another fire type but at least he's part fighting. His blaze ability is basically the equivalent of a super saiyan.
Squirtle/Corphish/Kingiler: Its fair game here since all the water types are pretty equally matched.... except poor unfortunate Totodile and Buizel is at least getting better. Squirtle has been in many matches and is responsible for many of ash's wins in the Indigo league. His Shades make him bad ***. Corphish can take hits and is pretty speedy. He's able to OHKO at surprising times as well. Kingaler evolved randomly during a tourny battle in the indigo plateu and won with no experience or training with Ash. Surprise win ftw.
Noctowl: When it comes to the birds this one becomes extremely hard to say when all the birds are pretty equal. I'd say Noctowl just cause it can still hit ghosts and is full of surprises. Noctowl all the sudden has a new powerful move pool that hits hard. The johto league does it no justice anymore and should be removed from its resume. Staraptor is able to pull off a lot of powerful moves including close combat but this comes with a double edge for its defences are lowered and Brave Bird hurts it. Swellow is good and the fastest of ash's birds as well as being in the same rank as Corphish. I would make Swellow another choice if it wasn't for it getting quickly beaten by Latios but perhaps that is too strict.
Snorlax: The final member and may seem odd but he has lost little to none when ever he is used by Ash which is odd since ash is usually more focused on speed. He has great power and an excellent recovery move. The only reason ash uses it less is because according to the anime hibernates for a long time and is unusable during this time. When snorlax is ready to fight, fear it.
This is just my oppinon and I'm sure there are better combinations of Ash's pokemon and more reasons for better team match ups but the way I see it, this is ash's ultimate team for whatever he faces.
Pikachu: This thing has defeated many powerful pokemon like Dragonite, Regice, and recently Latios. Ash just needs to use Volt Tackle less so its not sucj a kame-kaze.
Skeptile: Defeated Darkrai so major props for that and was able to tie with a Blaziken when it clearly had a disadvantage.
Charizard: Defeated Articuno and fought well against an entei with hax crystals.
Infernape: Another fire type but at least he's part fighting. His blaze ability is basically the equivalent of a super saiyan.
Squirtle/Corphish/Kingiler: Its fair game here since all the water types are pretty equally matched.... except poor unfortunate Totodile and Buizel is at least getting better. Squirtle has been in many matches and is responsible for many of ash's wins in the Indigo league. His Shades make him bad ***. Corphish can take hits and is pretty speedy. He's able to OHKO at surprising times as well. Kingaler evolved randomly during a tourny battle in the indigo plateu and won with no experience or training with Ash. Surprise win ftw.
Noctowl: When it comes to the birds this one becomes extremely hard to say when all the birds are pretty equal. I'd say Noctowl just cause it can still hit ghosts and is full of surprises. Noctowl all the sudden has a new powerful move pool that hits hard. The johto league does it no justice anymore and should be removed from its resume. Staraptor is able to pull off a lot of powerful moves including close combat but this comes with a double edge for its defences are lowered and Brave Bird hurts it. Swellow is good and the fastest of ash's birds as well as being in the same rank as Corphish. I would make Swellow another choice if it wasn't for it getting quickly beaten by Latios but perhaps that is too strict.
Snorlax: The final member and may seem odd but he has lost little to none when ever he is used by Ash which is odd since ash is usually more focused on speed. He has great power and an excellent recovery move. The only reason ash uses it less is because according to the anime hibernates for a long time and is unusable during this time. When snorlax is ready to fight, fear it.
This is just my oppinon and I'm sure there are better combinations of Ash's pokemon and more reasons for better team match ups but the way I see it, this is ash's ultimate team for whatever he faces.