On the one hand I'm always suspicious of lists, but it's always interesting to see what Variety has to say. As one of the few media outlets dedicating to covering film festivals worldwide they have a perspective that really can't be matched. Personally I don't have the means to treat this as a travel guide, but it will definitely influence where filmmakers will spend their festival submission dollars when they're done wooing Sundance and Toronto.
Notable inclusions: Indianapolis' Heartland Film Festival (dedicated to "beautifully made films that celebrate the positive aspects of life"), CineVegas (which cultivates its home town's "naughty nightlife image"), and Sitges ("Europe's biggest fantasy-film fest").