While I disapprove of Queen continuing, I like the choice of Adam Lambert such as it is. Personally I think there's more honor in getting another big artist in their own right to fill the role of a major player, as opposed to just getting someone from a tribute band. I think it's kind of disrespectful, to find the closest facsimile, instead of trying to move on as a band and carve out something of a new niche or era. Like Black Sabbath with Dio or Van Halen with Hagar. They weren't the same band but they were something that stood on its own and I respect that.
Like Alice In Chains for example... I have no interest in whatever they're doing with their new guy, he's just trying to copy Layne and he'll never succeed at that. But if they had gotten someone like Phil Anselmo (from Pantera) or even one of the big "nu metal" singers of the time, that certainly wouldn't have been the same old Alice In Chains we love, but it would have been a band I'd be very interested in listening to and giving a chance to.
I don't have a problem with classic bands touring the hits, but if you're going to lose a quintessential member, I think at that point it's time to try something new. I think that method pays more homage to the old band, to say "we know we can't replace you, so we aren't going to try. But we still love playing together, so we're going to try to move on and do something new with this band."