John Oates is showing love for his longtime partner turned legal adversary Daryl Hall ... calling him one of the all-time greats, despite the dispute that's blown up the Rock Hall of Fame duo.

The legendary singer-songwriter opened up about their early days recording together, telling the New York Post -- he ended up taking more of a backup singing role to Daryl because he quickly learned what an amazing voice he has.

John actually called his ex-partner one of the greatest singers ever -- extremely kind words, especially considering DH filed a lawsuit against John late last year.

Oates said he couldn't talk about their pending legal issues, but he did want to plug his new solo album, "Reunion."

He makes it clear the album's title isn't a subtle nod to him having any hopes of getting back together with his former pal -- John says it's just a coincidence.

As for what it was like recording solo -- JO says he's returning to an earlier sound that predates Hall, and he's really stoked about finally putting his creativity first rather than the band's ... which you could certainly read as a subtle dig.

ICYMI ... Hall sued Oates last year, claiming John secretly tried to sell his half of their shared company to a third party that Daryl doesn't trust. John's denied the claims, but has refrained from any mudslinging while the case plays out.

While John's taking the high road ... don't expect a Hall & Oates reunion anytime soon.