I've played a lot of fantasy mmporpg games with my group of friends. Most of which have dwarves (or dwarfs) in them. Its interesting to me, that a few times (from friends that don't regularly read fantasy novels) I hear they can't imagine why someone would pick a dwarf for their character.
I think this goes back to the over-all common tastes that have been bred in our culture of what is cool and what isn't. Or at least in Hollywood. Being short, over weight and broad isn't considered "cool" so why would it be portrayed as so? Thus, the abundance of dwarves regulated to comedy relief. Same goes for any minority considered "uncool" I think.
Even though I'm sure I'll seem superficial for saying this, but there are a lot of unsaid truths about most of us. No one wants to be ugly .... that part is true. Thus, the journey we want to take when we go for escapism, is a journey with an idealized character. Someone tall handsome, beautiful .... Not ugly. Or at least that's what Hollywood's first thought is -- But for those characters in both real life and in stories that aren't the archetypical handsome/beautiful icon , there are so many that have not let this be any handicap of any kind and have gone on to do great things. Why cannot dwarves (on the big screen) be brought into the same group of characters?
Perhaps the average movie maker hasn't read enough examples of cool dwarves like the rest of us fantasy fans?
Sure, Gimli did beat Legolas by one in his body count at Helm's Deep. But really, that and a few seconds here and there (in front of Helm's Deep gate with Aragorn stalling, alongside Aragorn and Legolas at Pelenor fields from the boat fighting inward toward Minas Tirith) are the only times he's just plain kicking butt and not being the brunt of a joke. MOST times he's being the comedy relief unfortunately.
I love the LotR movies a lot, but there are still things I'd rather of seen differently. Both Aragorn and Legolas get to have a showcase cool fight moment in each movie but Gimli not so much. Only dwarf in media I've seen be the type of dwarf I'm used to reading about in my favorite novels or rpgs is the dwarf Ghim from Record of Lodoss War. I've yet to see the type of dwarf we D&D fans are used to.