When Andrea Romano cast just right

That was Maurice LaMarche.

Don't forget Pyg. He was just perfect.

John Glover was the best voice for The Riddler. He had the perfect amount of intimidating smugness. Other voices always make him sound too geeky.

Ron Perlman is still the best voice for (Matt Hagen)Clayface.

Why did he turn it down?

No I think he had passed away by then.
But the replacement voice was pretty spot on.