The way I see it, the first two solo albums were fantastic, but then I heard some of his stuff after that and save for Band On The Run and Tug Of War, any of his work between 1972-1994 is pretty much hit and miss, like Catman said.
I don't know what happened, but from Off The Ground onwards, Paul has been killing it. Flaming Pie, Unplugged, Run Devil Run, Memory Almost Full all good to great albums, then there's his work with the Firemen which sounded really fresh. And in my opinion, next to Ram, 2005's Chaos & Creation In The Backyard might be his best album. So, if anything Motown, pick up Chaos. That one is a work of art.