I miss the cutoff by a year, so I didn't vote. As to the ERB tangent, I'll merely say that as a big fan of pulp fiction, I find the John Carter stories refreshingly FREE of the widespread racism that mars a lot of their contemporaries.
From the list, I've read...
Tolkien: I enjoyed The Hobbit a lot. I didn't much care for LotR when I first read it and vastly prefer the film version now. Obviously a giant of the genre and a great scholar, but his work became the genesis of the type of fantasy I loath and arguably of my loathing thereof.
Howard: My favorite fantasy author. A great stylist whose vibrant and energetic - and sometimes surprisingly spare, for the era - prose perfectly matches the savage worlds and characters he created. Solomon Kane may be my favorite character in fantasy.
Pratchett: On the other hand, Howard has some serious competition. I rank Pratchett as his equal as a favorite author, but lower as a FANTASY author because the fantastic elements of Pratchett aren't really to my liking (with some exceptions). Pratchett's humor, characterization and storytelling are all tops, but his actual fantasy is straight-up parody, much of it of works I dislike.
Mieville: I've read Perdido Street Station and The Scar, and liked the second better. A true current-gen fantasy great, albeit not one I particularly enjoy compared to some of his contemporaries. Like Tolkien he builds an amazing world, and his is more interesting to me. On the flip side, I experience at least as much values dissonance with his odd 19th century Marxism as with the pulp greats, and unlike many more modern authors he's at least as heavy-handed with it.
Vance: I've read the Complete Dying Earth. I enjoyed it, but not hugely.
Moorcock: Stylistically uneven, with a core narrative weaving through much of his work that justifies, even expects, repetitive themes and even characters. Despite all that and cramming WAY too many Elric stories into WAY too little reading time a few years ago, I find I actually enjoyed many of them quite a lot, and will continue to read more of his work.
Lieber: I expected to love Lieber but actually merely like his work, kinda. I'm not sure what it doesn't have that I was looking for.
Jordan: The only Jordan I've read is the very beginning of the Wheel of Time and half of one Conan pastiche. The former helped turn me off of an entire generation of epic fantasy (not that I needed much help), the latter made me practically gag as a Howard fan. Blech.
I haven't read Brooks or Rowling. Brooks because I dislike the type of fantasy he writes. Rowling because I'm only really interested in Harry Potter due to the popularity of the series (its subject matter being pretty well outside my area of interest) and have been, almost inevitably, suffused with spoilers. I've read snippets of all three and only Rowling appeals to me as a writer.
If you were going for five major writers of MODERN fantasy, I'd say only Pratchett, Rowling and Mieville belong. Brooks and Jordan fall into the previous generation, and George Martin is much more famous today than either.
Other important 'current-gen' writers include Sussanah Clarke (Jonathan Strange and Mr. Norrell), Neil Gaiman (Neverwhere, American Gods), Brandon Sanderson (Mistborn, Elantris), Jim Butcher (Dresden Files), Naomi Novik (His Majesty's Dragon). Butcher's work inspired a TV series, Novik's is under consideration for a movie deal by Peter Jackson, and Gaiman's rep from both books and comics is sufficient to get his name as a writer to headline major motion pictures. Clarke is more of a literary pick, and Sanderson probably doesn't belong in a top five list if you're going by fame.
If I had to pick a who's who Top 5 of modern fantasy, I'd say:
Rowling
Pratchett
Martin
Gaiman
Butcher