In looking at their songwriting partnership, Lennon and McCartney were perfect for each other. Lennon would add an edge to Paul's penchant for throwaway lyrics and let him know when a song wasn't good (Lennon was said to have hated "Maxwell's Silver Hammer" - and rightfully so. He refused to participate in the recording of it). I also don't believe John would've allowed "Mary Had A Little Lamb", to see the light of day. Paul would rein in some of John's over the top songs ("Cold Turkey" and "Mother" would never be allowed to appear on a Beatles album) and add melody to them.
Many people have different opinions on this topic, but I believe Paul was unfairly portrayed as a soft music artist, who was riding Lennon's coattails. Let's be honest. John was martyred after his death. If one were to look at the last three Beatle albums, John Lennon had mentally checked out.
John famously complained in a 1970 interview with Lennon toadie Jann Wenner of Rolling Stone that the band had tired of being sidemen for Paul. Other than being strung out on drugs a lot of the time, what did Lennon really contribute during 1968-69? "Revolution" is an outstanding song, as is "Don't Let Me Down". "The Ballad of John and Yoko" is, narcissistic, but excellent as well. That's pretty much it.
During the last 3 albums, some examples of the contributions from Lennon were "Happiness Is A Warm Gun", "Everybody's Got Something to Hide Except Me and My Monkey", "Revolution 9", and "Come Together". Those don't come close to measuring up to his best songs. Paul McCartney's songs during that time frame include, "Let It Be", "The Long and Winding Road", "Golden Slumbers Medley", "Get Back", "Oh Darling", "Back in the USSR" - all Beatle classics.
It is obvious who wrote the better songs during those last albums. By Abbey Road, the Beatles turned into the Paul and George show. The two biggest classics from Abbey Road, are "Something" and "Here Comes The Sun" - both by George Harrison.
Sgt. Pepper's Lonely Hearts Club Band is considered by most critics to be the greatest album of all time. John Lennon readily admitted that the ideas behind the album came from Paul. John did contribute the great, "A Day In The Life", with the perfect middle part of the song written and sung by Paul. That is songwriting collaboration at its finest.
Now when it comes to the early Beatles material, I believe John Lennon's songs were much stronger. His contributions on the "A Hard Day's Night" album are a tour de force, too many to list. Other early Lennon songs, "Help!", "Please, Please Me", "Norwegian Wood", "Nowhere Man", and "In My Life", are some of the biggest Beatles songs.
In terms of their solo material, they badly missed one another. Both had their hits and misses. Paul has missed the mark badly, several times. Albums such as "Wild Life", "Red Rose Speedway", "London Town", "Pipes Of Peace", "Press To Play", and "Off the Ground" are only for the truest McCartney fan.
Lennon's penchant for radicalism and political songs went way over the top, thus leaving some of his material, such as the album "Some Time in New York City", unlistenable. I'm also not much into the tortured artist persona. I listen to music for enjoyment, not to hear songs like, "My Mummy's Dead", or bizarre material such as "Don't Worry Kyoko (Mummy's Only Looking for Her Hand in the Snow)".
To me, there are four songs that are the essence of John Lennon's solo career.
"How Do You Sleep?" - from the Imagine album. A postcard of disdain to Paul McCartney featuring lyrical put downs with titles of McCartney songs. A slow bluesy type song, featuring a killer slide guitar solo, cheerfully delivered by George Harrison. In an interview a few years later, John attempted to back off the obvious fact that this song is about Paul and but instead was about himself. Yeah, sure.
"God" - John's song about what he believes and his standing in life when the song was written in 1970.
"Jealous Guy" - This song is my favorite solo song written by John. Where was this type of song in 1969?
"Stand By Me" - a cover song on the Rock n Roll album, but the song is sung with such a fantastic edge, it is truly a tremendous performance. This version blows the Ben E. King original away. This is Lennon singing and performing at his finest.
It is unfortunate that Lennon took 5 years off from music in the last years of his life to raise his son Sean. Maybe he felt he needed to be the father he wasn't to his other son Julian, or he had tired of the music business, or even had writer's block, no one will ever know for sure. Yoko Ono certainly won't tell the truth about it. It wasn't until 1980, when John heard Paul McCartney's "Coming Up" on the radio, a song which he supposedly loved, that he was inspired and spurred to start writing again.
Lennon's last album, "Double Fantasy", features strong material such as, "Just Like Starting Over", "Beautiful Boy", and "Watching the Wheels". Unfortunately, the album consists of several Yoko Ono songs. The song "Woman" is as sappy as any love song Paul McCartney ever wrote. Yet, Lennon never was taken to task for this, due to his death. Instead, Paul gets grief for "My Love", which is a better song than, "Woman".
Taking Yoko Ono out of the equation, if a Beatles reunion were to ever occur, I believe the one they would've had the hardest time getting on board would've been George Harrison. George didn't enjoy playing the part of Beatle George, and despite Paul's public appeals to the contrary, George was not a big fan of Paul. Even during the 1994 Beatles Anthology in sessions, there was tension between the two. He always felt marginalized by him. If you've ever seen the movie, "Let It Be", you'd understand why George felt this way. You'll see Paul in action, behaving like a jack ass throughout the movie.
Fortunately, both Ringo Starr and Paul are still around and still touring. Paul still sings great, plays super, critically acclaimed shows, and carries the Beatles legacy on his back. It's obvious he's still stung by the criticism he's received in the wake of John's death, by the number of Beatles songs he plays in concert (including Lennon and Harrison sung songs) as well as on the 2002 Back In the US live album, changing the songwriting credits to McCartney/Lennon.
Paul finally came to terms with the criticism he received for some of his Wings material (and yes, he deserved to get hammered for some of it), that on his 2010 tour he expanded the number of Wings songs on his set list and has added songs never played live before, as well as some songs that haven't been played live since 1976.
So, the legacy carries on - minus two members, the albums still sell millions of copies all these years later, and the "what if's", about what could've happened to the greatest music group of all time continue on, 40 years after the group broke up.