In past seasons of the Pokemon anime, Ash has brought back some of his classic Pokemon to aid him on his journey. While perhaps the case with his mother's Mr. Mime finally getting some battle attention, there have yet to be any of Ash's old Pokemon brought back for his team during Pokemon Journeys.
While classics like Ash's Charizard seem like the obvious choice to bring back, there are more of Ash's Pokemon who deserve their chance to shine. Whether they're Pokemon who could benefit from more time with a more-experienced Ash to hone their skill, or Pokemon who are ultimately just great fighters who could help Ash climb the ranks, these Pokemon are worthy of another shot to journey alongside Ash once more.
10 Incineroar
Incineroar is a Pokemon fans saw very little of in its final Evolution, having evolved after the final match of the Manalo Conference against Professor Kukui. In fact, it never got to battle after its Evolution, since swiftly after Ash's victory he left it in Alola. As such, its capabilities as an Incineroar were never fully explored, and judging by its battle abilities as a Litten and Torracat, it would certainly prove a powerhouse of given more attention.
Plus, adding Incineroar to his final team would allow Ash to capitalize on its added Dark typing. With a moveset that already features Fighting and Fire moves, the additional dip into Incineroar's Dark-type moves like Darkest Lariat or Throat Chop would make Incineroar effective across the board.
9 Snorlax
Without a doubt, Snorlax is one of Ash's most capable Pokemon in battle. While its laziness and fixation for food have gotten in its way before, it has, on multiple occasions, gotten out of this mindset and gained Ash a victory. It is undeniably a lovable Pokemon outside of combat, and would make for an affectionate partner for its fellow Kanto Pokemon on Ash's current team, Dragonite.
Because it was added to Ash's team so early on in his Pokemon journey, it perhaps didn't get used to its full potential due to Ash's inexperience. Now a more seasoned trainer, Ash could utilize the huge arsenal packed into the Sleeping Pokemon. What's more, adding Snorlax to Ash's team could allow for a chance to see another one of Ash's Pokemon Gigantamax.
8 Glalie
Evident during the Ever Grande Conference, Glalie is a Pokemon that can hold its own during battle. It has withstood battles when at a type disadvantage, and would occupy a missing space on Ash's team with Ice-type moves.
Despite Ash initially wanting to use Glalie during the Lily of the Valley Conference, he ultimately opted against it, not wanting to rely on sheer power. As such, this Pokemon deserves much more attention, given that Ash acknowledged how powerful it is. With Lucario and Gengar in rotation as well, there's a chance Ash could create a combination of Mega Evolutions (should the anime ever go in the direction of Ash finally getting a Mega Ring).
7 Totodile
The energetic Big Jaw Pokemon was one that had to fight for Ash's attention alongside the other Generation II starters (who both evolved, unlike Totodile). As a comic-relief character in the anime and worthy fighter throughout Ash's journey in Johto, it would fit well alongside Ash's current party and match the narrative direction Pokemon Journeys has been going on.
Ash saw huge success with Greninja, another Water-type Pokemon. Given that Totodile has spent so much time with Ash and is a practiced Pokemon, it could bring Ash success once again and finally get the chance to evolve, putting itself up there with the likes of Charizard, Sceptile, Torterra, and Greninja as a successful starter Pokemon.
6 Gible
Although Ash already has a Dragon-type Pokemon in his line-up with Dragonite, seeing the adorable Land Shark Pokemon return would be both beneficial for battle and entertaining for fans. With Ash bringing so many past Pokemon back for the Lily of the Valley Conference, and the fact that Gible was his last caught Pokemon in the Sinnoh Region, the Pokemon didn't see a ton of growth beyond learning Draco Meteor.
therefore, the possibility of Ash adding it back into rotation, and potentially seeing it evolve into the devastating Garchomp, could be strategic for him. Plus, it would be satisfying to see this clumsy, destructive Pokemon mature into a seasoned fighter.
5 Kingler
Kingler was Ash's first experience having a Pokemon out of rotation due to the six-party maximum. Because of this, it was often left with Professor Oak, and did not see as much attention as his other Kanto Pokemon. When it did eventually evolve during its first battle, it proved time and again to be an excellent battler in Johto.
While Kingler has made several reappearances, they have all been non-battle related. As a silent, determined fighter, it could grow to be a major go-getter — so long as Ash finally focuses on its skills. Additionally, Kingler has also gained more attention, being given its own Gigantamax form, which could bode well for Ash transitioning it back into his party.
4 Bulbasaur
One of Ash's original Pokemon, Bulbasaur has often taken the backseat to Ash's relationship with Charizard and has never gotten the full recognition it deserves. The Grass-type starter was always one of Ash's most mature Pokemon, one that proved to be a leader amongst all of them.
In spite of making multiple reappearances, Bulbasaur hasn't been in rotation since Hoenn, but given its consistent strength, bond with Ash, and overall experience, it could take the mantle once again as a leader on Ash's team. Not to mention, it would be satisfying to see a Pokemon from Ash's original journey come back and be utilized better with Ash's newfound skill.
3 Melmetal
Another Pokemon from Alola that saw minimal battle time in its final Evolution, Melmetal demonstrated natural battle potential in its heightened Evolution form. As a Melmetal, it overpowered opponents with its raw strength, but unfortunately lost on two occasions due to type disadvantages.
With minimal time spent training as a Melmetal, it could perhaps benefit from more time with Ash, helping it accustom battle strategies to its bigger stature and strength boost. Pairing it alongside Incineroar would be deadly, and the two would make excellent sparring partners (along with Lucario).
2 Scraggy
Unova saw Ash have nine Pokemon in rotation, being the biggest team he's had. But what comes with this many Pokemon is the chance for some to not get as much attention as the others. Such was the case with Scraggy, who remained in its first Evolutionary stage the entire time it spent with Ash.
Despite its size and inexperience, Scraggy was one of Ash's most successful battlers in Unova. With a hardened resolve, its growing maturity was cut short due to Ash embarking on a journey in another region. Being the only Pokemon that Ash hatched from an egg to not evolve, journeying with Ash again could result in both an evolution and improved battle prowess, already building off of Scraggy's evident potential.
1 Infernape
Of the many starter Pokemon Ash acquired on his journeys, Infernape is perhaps the most successful fighter, rarely losing any battles. From its tragic time recovering from its abandonment to its numerous victories with Ash, Infernape is without a doubt one of the best Pokemon he has in his arsenal.
What ultimately sells Infernape as a great re-addition to Ash's team is its combat knowledge. It utilizes its Blaze ability (and has learned to control it), has an array of moves with different types, is unafraid to take on a challenge, and generally meshes well with Ash as a trainer. Also keeping in mind the recent announcement about Sinnoh remakes, it would seem fitting to add a starter from that region back to capitalize on this development.