I first saw Queen in 1978 in Frankfurt and it was the first big concert I ever saw. I was quite impressed. Freddie's death was a big loss for all rock fans, and in my opinion he had such a unique voice that it's impossible to replace him. Queen without Freddie doesn't sound like Queen anymore.
Lambert does a bloody good job, and boy, he can sing! But he reminds me more of the lead singer of an 80s band called Europe.
I think most vocal replacements don't work. AC/DC may be an exception, but Bon Scott's voice is THE AC/DC voice imho.
I saw YES concert videos with some young guys trying to replace Jon Anderson, and it was really poor, although they can sing, but there is no spirit anymore.
Imagine Led Zeppelin without Robert Plant! Ridiculous!!!