Obviously Paul's solo career is the 'most successful:' Most hits, another successful band, many huge tours, etc.
But I still prefer John's catalogue. And for jjs, who seems to have an irrational dislike of John Lennon, you made a few erroneous points. John couldn't do it by himself? What's that supposed to mean? His best solo work stands up to his Beatles work. Sure it was uneven, but so were the solo careers of the other 3. (I personally love John's Double Fantasy songs -- Woman, Watching the Wheels, Beautiful Boy, Just Like Starting Over.... maybe you don't. That's your problem.) John couldn't fill up a stadium? When did John decide to do a solo world tour? If he had, I think he would have filled stadiums. But apparently Beatledom had permanently soured him on tours. Can you blame him? Did he need the money, or the aggravation at that point?
JJS has no dislike for John.
JJS dislikes the notion that his solo career was somehow rendered "more important" than it actually was, solely because of his political views. As I said, no one can compare John's solo career to Paul's in any way where John comes out on top. So this ridiculous notion was invented.
I prefer to judge his (and the rest of the Beatles) solo careers without all that silliness.
"John couldn't do it by himself? What's that supposed to mean?" It means that John couldn't crank out #1's singles like Paul could. His only #1 single was "Whatever Gets you Through the Night"... with help from Elton John. Part of the reason the Beatles broke up was because John was sick of "being a sideman for Paul." He was upset because Paul got the "A" side while his songs got the "B" side, although personally I don't see this. After the Beatles, John's singles didn't hit the top of the charts... and then of course when the #1 hits weren't coming so easily, such "commercial" success suddenly became unimportant.
"John couldn't fill up a stadium? When did John decide to do a solo world tour? " John toured early on... and his management company quietly bought up empty seats. No one could trust they weren't going to get 45 minutes of Yoko shrieking.... so his attempt to play concert dates flopped. George also had a failed tour in the mid 70's.
I like "Double Fantasy". IMO, songs from these sessions were among the strongest written, most consistent, and best produced Solo-Beatles material (I tend to combine DF and M&H sans Yoko.) I think "Cloud Nine" is similarly strong, and "ATMP" too.
I've written endless posts with my opinion that Paul's solo songs almost always sound unfinished to me, and that his lyrics most often seem like unrelated phrases that "allude" to a point without ever actually making it. I also don't care for the mushy production on his albums either. Jack Douglas' job on "DF" ranks as my favorite solo album production.
I'm not playing favorites here... Just telling it how I see it.