To begin with ,most royal brides' dresses were classy,but simple in itself,as it concerns my tastes I rather prefer more unusual ,vintage or gothic styles(Vivienne Westwood) to the simple ones,but to keep class and originality it's not a simple matter .The celebrities used to have more specific dresses than royals,anyway I'd think it's better to avoid tacky models.
My general preferences go to Nicole Kidman,Jacqueline Kennedi,Celine Dion,Gwen Stephanie and Dita Von Teese styles.Or I prefer styles like this one:
http://www.weddingtemplates.net/wp-content/uploads/2010/08/silver-wedding-dress-1.jpg
But from the royal brides' dresses I put them in this order of preferences
1.Princess Grace of Monaco timeless style
2.Princess Mary of Denmark
3.Sarah Ferguson(though I'll prefer more strapless modern variant of it)
4.Princess Maxima(I especially like her tiara in combination with all the outfit)
5.Kate,Duchess of Cambridge
6.Isabella Orsini
7.Lady Helen Taylor
8.Duchess of Kent
9.Princess Diana(ideal model for a virgin and very young bride)
10.Princess Marie of Denmark(coquette ,but showing dignity at the same time)
11.Tessy of Luxembourg
12.Princess Letizia
The other models I didn't notice or they are not in my taste at all.