There are a number of reasons why people don't like Bosmer, I'd say. The cannibalism might have something to do with it, but to those who haven't done that much research, it would also stand out that in both Morrowind and Oblivion, Bethesda decided to give their males very annoying voices, and made many hated characters in the games Bosmer, so it's to be expected that some wouldn't be too fond of them.
Personally, though, I don't like any of the elves in the Elder Scrolls. Elves are just such a cliche and overused fantasy concept, and really, it's hard for me to take any race that shares a name with the little guys that make toys for Santa Claus seriously, and really, I never got what the obsession certain fantasy writers have with races that are basically humans except with different body proportions, facial features or funny shaped ears. It's just such an uncreative and boring way to make non-human races in your setting. The least they could do is change the color of their skin. If you're not going to even try to make race designs that will stand out, you might as well just not bother and just have different human cultures. And the lore written for the Elder Scrolls elves that aims to make them different from typical elves often instead just makes them even more unlikable to me, I mean things like the Bosmer's cannibalism or the Dunmer's slavery. Maybe these things wouldn't be so bad if they were villains, but it's rather hard for me to relate to a culture that eats their own dead or enslaves other races as the "good guys".
As for the cannibal thing...what's worse, the mere eating of their dead as a respect issue, or that other Dunmer "quirk" that the woman in Oblivion skirts in conversation with her "let's just say this wouldn't be the first offense..", (parap). Eat the dead, or shag them? I'll take the barbecue for 200 Alex.
The difference here is that cannibalism is an aspect of Bosmer culture, whereas the other thing seems to be just a quirk of that character, and in fact is probably punished quite severely in Dunmer society, as indicated by her dialog when you tell her that it's at least 500 gold in Cyrodiil and she says it's much less than Morrowind.
I beg to differ. Dwarves are a great example. A typical Dwarven race will tend to have amazing smithing skills, and are usually an honour bound race. Even with thier stumpy posture and scottish acents, companies often make Dwarves seem just as cool as any other race. This is because it's usually recycled lore from other media, and it isn't hard to recreate a good Dwarven race. I think World of Warcraft ad great lore on the Dwarven race, for example. Bosmer had difficult lore to work with. How can you create a civilised race of cannibals?
I don't know, I have a pretty hard time taking dwarves seriously in most games. Though it's mostly because of all the cliches that always surround them rather than that they're short. Although there have also been some examples of dwarves in comic relief roles.
Also, did anyone have any trouble taking the Hobbits in Lord of the Rings seriously simply because they weren't as big as other races? I know I didn't.