Well, no one of the ex-Beatles had a "complete triumph" in his solo-career (who can claim so anyway ?). Personally, I've never heard or read any suggestions that John's (short) solo-career was throughout successful. Besides, I don't think it's the point of such an album-analysis to evaluate the music by sold-albums or chart-position.
Your right snoopy, collectively the fabs were monumentally fantastic, the best best in the world by miles, STELLAR.........even their poorer albums were triumphs, as solo artists they were ordinary, crappy, boring and completely uninteresting, even Johns best LP Imagine was average at best. And as for Paul, just catchy chart obsessed teen girly nonsense (he had no-one to tell him no anymore), Georges stuff was preachy self obsessed and droning and Ringo well, he's just Ringo, singing cast offs from the others.
My views entirely of course