... It's the CREATURES, dude!!!
Haha, yeah... In my mind, it's the creatures that really make a fun fantasy novel.
Sure, you're probably thinking... "vamps, werewolves, dragons, dryads, goblins... so how does that make or break a story?" Well, I'm not really talking about those kinds of creatures. I'm not saying that dragons or werewolves aren't awesome - quite the opposite, they're popular for a reason! But it's the unique creatures, the ones that the author has made up to fit their own little fantasy world, that make reading a fantasy novel really cool.
One of my favorite examples of this is Kate Forsyth's novel "The Witches of Eileanan". I was kind of annoyed with the main character (she was described as spunky?? Are you kidding me?!), the writing style made the story hard to follow, and the neatest character of the bunch was getting tamer, not the other way around! But I couldn't put it down because her creatures had totally captured my attention. Though they didn't play a huge role, she'd populated her world with elven cats, dragons, Mesmerds, and all sorts of other interesting animals. By far, I'd have to say the Mesmerd was my favorite... a swamp creature with big eyes, a bunch of arms, wings, marsh-grey skin, (overall, it looked like a sleek, oversized Gollum... a bit) a breath that kills, and a mission to steal young children - how could that not be riveting?
So yeah... I'll admit, some of my stories are just excuses to make up my own fantasy creatures. Preyteons, Satarri, Kine, Kridh' - ah, I have so much fun with them. And even the creatures that aren't totally my creation are fun to play with, like weredragons, wind dragons, sprites, shapechangers, Elementals, and vampires... I could go on and on, but you've probably heard enough.
Try it sometime... just pull out a piece of paper and start sketching, or watch a movie and let your imagination run wild, and see what sort of crazy creature you can come up with!