If we are talking just title tracks then my ranking would be
1: Solo
2: On The Ground
3: Flower
4: Lalisa
My favourite song is Gone out of all the solos, but I honestly think the difference in the quality of their solo songs vs group songs is insane. I've kind of thought they where all not great on the first listen to be honest. I warmed up to Solo very quickly, but I'm still hoping Jennie gets to release more solo music in the future, as she has the most potential for bops in my opinion.
I didn't like On The Ground when I first heard it, but its actually something I listen too regularly now and I adore Gone I feel like that song is made perfectly for Rose. Lalisa is honestly one of the worst solo Kpop songs I've heard, and Money is awful in my opinion too, I had much higer hopes for Lisa. Flower whilst visually its nice, and I clicked with the song much faster than Rose and Lisa, I dount I'll listen to it much in the future.