My opinion, for what it's worth:
The styles of writing in The Hobbit and the Silmarillion have always had that same difference to me. I often think of The Hobbit in terms of a storybook, and the Silmarillion in terms of a history book.
Though I must say that I prefer the Silmarillion to most history books. Much more interesting, despite the huge amount of strange Elvish names just waiting to be mixed up.
But, of course, a place described in a storybook and a place described in a storybook are usually going to sound that way. History books are dealing with (sometimes Dark and Drab) Serious Subjects, and therefore sound Serious. Very serious. Storybooks usually make the good parts sound very, very good, and the bad parts sound very, very bad; therefore Gondolin, being good, sounds very, very good in the Hobbit, while in the Silmarillion it sounds more serious.
I like both ways of looking at it.