I've thought a good bit about this actually, but my pick is Kenny Omega.
His catalog is about as good as it's ever going to get for someone who never appeared in WCW or WWE. Has legendary matches and runs in singles, tag team, and six man/trios team. Led one of the greatest factions that ever existed in Bullet Club. His opponent catalog is basically a whos who of grapplers from outside WWE.
I feel like his catalog as a tag team wrestler puts him over the top of others I would consider. It's very rare these days to see someone have high caliber tag team runs once they have established themselves as a top flight singles competitor.
I get lengthy runs in AEW, New Japan, DDT, ROH.
I get shorter but good runs in All Japan, PWG (2009 Battle of LA Winner), Impact, AAA
I get all his multi-man matches with the Bullet Club and The Elite
I get his tag matches with Kota Ibushi as the Golden Lovers, Young Bucks, Adam Page, and his other various Bullet Club partners
His rivalry with Okada was amongst the best in wrestling history
I get matches against Okada, Ospreay, Naito, Ishii, Young Bucks, Ibushi, Bryan Danielson, Tanahashi, Kushida, Elgin, Kojima, Rey Fenix, Alex Shelley, PAC, Shibata, Mascara Dorado, Austin Aries, Takeshyta, Davey Richards, Kenny King, Prince Devitt (aka Finn Balor), the Briscoes, Penta, Tetsuya Endo, Moxley, Roderick Strong, Cody, El Generico (aka Sami Zayn), Ricochet, Jay White, Jushin Thunder Liger, Zack Sabre Jr, Claudio, Hangman, Christian, Christopher Daniels, Marty Scurll, Kevin Steen (aka Kevin Owens), Taka Michinoku, AR Fox/Killshot, Dragon Lee