I would agree Banks was the weakest voice in the cast. She just didn't seem to get into it like the others.
Morgan Freeman was brilliant as always, especially with his more humors lines.
Chris Pratt and Charlie Day both did great at their happy go lucky characters, Pratt even nailing the somber moments.
Will Arnett was a great choice for Batman, I don't think it would have been as funny had they tried to get Conroy.
Alison Brie was probably the highlight of the voice cast as Princess Unikitty. Nailing both the wacky parts and going full on feels with the destruction of her home.
Even the rest of the supporting cast with Metalbeard, Superman, Green Lantern and the Star Wars folks all did great (who wasn't happy to hear Billy Dee Williams out of nowhere).