Here, I made you a playlist of all Beatles solo material songs that are instances of both just good solo songs, as well as encompassing the lions share of any and all final solo Beatles collaborations.
I love "I'm the Greatest" because of how Beatles funny it is and because you its a Ringo song written by John, and with backing vocals by both John and George (they play guitar too).
"Every night" is just a beautiful song by Paul really indicative of the direction they probably would have gone had they stayed together. I know that Paul joked that ELO is what the Beatles would have sounded like, but that was a comment made waaay after the fact when the remaining Beatles were collaborating with Jeff Lynne for Anthology. Really, for the first few albums after Let it Be, Paul was really concerned with his domestic life (which John commented on. Really, of Paul solo songs he admitted to enjoying, the majority are fun in nature and domestic in theme, such as 'Every Night' and "Eat at Home" [he was also a big fan of "Coming Up," allegedly the impetus behind his emerging from being a househusband]). Had they stayed together, John and Paul songs would have been more mature and adult in lyrics and content with a focus on their marrages and growing up, and yes, inversely, I feel that when they wouldn't be writing those sort of songs, they would have been as silly as they've ever been (Wings, John & George's collabs with Ringo, Ringos stuff, and the stuff John did with Harry Nilsson attest to this. They would have written some corny stuff).
The real outlier would have been George. By and large he had for the immediate period after the most succesful solo career, both perceptually and arguably artistically (I believe commercially as well). We can't underestimate how in George's sort of pan-spiritualism and folk-guitar-rock fingerpicking were at about 70-72. He was yuuuge. So any scenario where even just for imagination sake we imagine him staying, he would have been still been releasing solo albums (All Things Must Pass probably wouldn't have been so gargantuan).