D4DJ is pretty sick but needs some stuff ironed out before I could recommend it wholeheartedly, but it's still worth a try if you're curious. Has by far the largest song list out of all these games and it's only 6 months into its lifespan, so the future looks bright, and the songs by themselves aren't bad at all. All of the girls are really fucking hot, too (if that's a plus for you).
Project Sekai also plays pretty smoothly and has a great difficulty curve, but the song list by itself is mediocre and that's not going to get better any time soon if their release schedule is anything to go by.
Bandori may feel somewhat dated now, but it does its own thing and it does it pretty well. It's been getting some updates to bring it to par, and it won't be dying any time soon. Corona and ProSeka getting most of the attention from the developer kind of messed up its update schedule though.
Tokyo 7th Sisters and [email protected]
Cinderella Girls Starlight Stage (what a mouthful) are pretty old but good nonetheless. I can recommend the latter personally, had years of fun with it even if some of its design decisions come off as odd. By now it has like 5 different play modes and a decent track selection that you don't need to go through the effort of unlocking (mostly) or anything like that.