The-Bloody-Bishop's avatar
Not only is blue perhaps the most popular color these days, but her 'tomboy' personality is also attractive to a lot of people. Rainbow Dash commands and receives respect for being talented and awesome, so its natural that she draws a lot of people's attention. Which is a pity, since I feel that characters like AJ or Rarity are more realistic role models to aspire too, since they're both successful, proud and happy in their professions, and actually encounter conflict within their profession. Rainbow Dash, on the other hand, is so skilled that flying is second nature to her; her conflicts don't involve flight itself, but loyalty or her self-image.

But I'm probably being unfair to all three characters at this point; in the show, at least, they've encountered enough of their own share of problems and overcome them to deserve the attention they receive, if not more so in the case of Rarity and Applejack.