Boris Gudenuf
Deity
@Boris Gudenuf Sorry, but no fictional universe will ever be more perfect than Middle-earth. Curse you, Tolkien, for writing the perfect story forty years before I was born, and for simultaneously creating a genre but doing it so well that no one else has ever even approached the bar you set for the genre! (It's actually kind of interesting that there's nothing like it in its cousin genre, sci-fi. I could name any number of works that were foundational to sci-fi or are giants of the genre, but none of them casts such a long shadow over sci-fi as Tolkien's legendarium does over fantasy.)
No question that Tolkien had and has absolutely matchless influence on the entire fantasy genre. The problem is, his influence was so overwhelming, that for 20 or more years you kept reading the same Tolkien-esque stories over and over again. The same Elf, the same Dwarf, the same Great Dark Overlord of Evil In His Dark Mountain and yadda yadda yadda. For a long time I kept an oath I'd made to myself to never buy or read another book with Dragon in the title Because I Was So Sick Of Reading The Same Book Over And Over.
It's gotten a little better now, with folks like George Martin and Guy Gavriel Kay doing some very different things with the genre and being really good writers to boot.
But, and this is my answer to why I research and write History instead of trying to write Fantasy:
Imagine a Great Dark Lord of Evil: he attacks his neighbors, enslaves their soldiers, burns their towns and palaces... And corresponds with every intellectual in the country, plays the flute and writes music - I just described, briefly, Friedrich II (Der Grosse) of Prussia: the fantasy genre very rarely shows enough imagination to equal what history can throw at you...
Oh, in Sci Fi, although not in one work, but Robert Heinlein's body of work probably had as much influence on classic Science Fiction: virtually every Trope of the genre - he did first: the time-travel paradox, the sub-light multi-generation ship, the Immortal going from ancient history to the future, the Future Soldier, the Other Planet Colony and Colonists - he was first and set the pace for almost everything everybody did afterwards.