Applicability: The movie works because it doesn't matter if you are not Greek, every family has a series of quirks that make it hard for outsiders to get on the inside. You can include almost any number of variations of ethnicity and religion into the title and the movie largely comes out the same.
Family-Unfriendly Aesop: The unwanted fuss over Toula's wedding can come off as "What your groom or you wants in the wedding doesn't matter, so feel free to change anything and everything about it to suit your family." However, it's also often Truth in Television.
Hollywood Homely: Partly averted in that, while certainly attractive, Nia Vardalos is anything but "Hollywood beautiful," and her "homely" look was genuinely convincing.
Roger Ebert: Everyone in this movie looks like they could be a real person. The romance involves not impossibly attractive people, but a 30-year-old woman who looks OK when she pulls herself out of her Frump Phase...I relaxed, knowing it was set in the real world, and not in the Hollywood alternative universe where Julia Robertscan't get a date.
Hype Backlash: My Big Fat Greek Wedding reached levels of popularity that are almost unheard of for an indie film. Because of this, it did have some vocal detractors who felt that received a lot more attention than it deserved.
Sequelitis: While the film might not be universally beloved, it's still a hell of a lot better regarded than My Big Fat Greek Life, which is regarded as one of the worst television spin-offs ever to be made, and among the worst major network sitcoms of all-time.