Dragons seem to be portrayed as very intelligent, even godlike and near immortal beings with magic. Sometimes they hate humans, sometimes they help them and sometimes they are neutral, but they are ultra smart and powerful, if vain and greedy.
Or they are portrayed as cunning and powerful animals of some kind, but not fully intelligent.
For some reason, video games often portray dwarves as having Scottish accents. A bit odd, considering their importance in Norse mythology. Also, female dwarves were often nonexistent or invisible in classic fantasy, though this has changed somewhat in recent years.
Elves are sometimes, though not always, portrayed as being more matriarchal than humans, or at least as having a society where the women are "allowed" to do the same things as the males. Of course, fantasy has shifted a lot in recent years, and you see more flexibility in gender roles. Elves of both genders are generally portrayed as gracile, beautiful, slender and fair-skinned.
And of course, elves are generally portrayed as being closer to nature than humans and as being immortal or at least very long lived, and therefore very slow to breed (so their numbers recover slowly from wars). They tend to be portrayed as a rather sympathetic race in modern fantasy, even sometimes as a race that is being encroached on by the faster-breeding and short-sighted humans.
There are some interesting stories out there where elves are portrayed differently than this, though. The Broken Sword by Poul Anderson comes to mind. I think he drew more from the old-style notion of elves being soulless Fae creatures who were largely hostile towards humans.
Also, Mercedes Lackey and Andre Norton co-write an interesting series of books (and darn, the name is eluding me now, because it's late and I'm too lazy to go look for them in my stuffed-to-the-gills library), where Elves were mostly evil beings who enslaved humans, while dragons were the wise, civilized race who helped right the wrongs.