>>22277579Izuru, Astel, and Rikka are generally the three people mention as the best singers. Rio with more practice will probably slot there too in the future. He desperately needs the flight time.
Having said that, Stars' singings have their own 'motives'. The other Stars are still better with their songs, just not as general as the aforementioned four + maybe Shien.
I think I can say there are people like me who loves Robesan's performance in the concert the most even though he barely sings. That was geniunely good, not only "good because you watch them the most" type of stuff I get from watching the girls (which is fine too).