Who says we dont have enough examples of ideal marriages ! Just the parameters of idealism are variable, hence the term is subjective !
Now, thats a myth that a successful marriage has to be ideal !! It has also been nicely explained by Poonam ....... and we dont find iconic examples because we have never tried to find icons in this field too. If you do, you will surely find many.
There are divorces, there are failed marriages, but just like few specimens of bad parenting cant rule out the importance of 'parenting' as such, similarly, few divorces cant rule out the importance of a 'shaadi' .......
Ye wo ladoo hai jo khaaye wo bhi pachtaaye, jo na khaaye wo bhi .......... ye aise hi nahi kaha gaya hai shayad ! ......... ye aisa ajeeb type ka ladoo kyo hai ?? :p
Well, failing of few marriages dont mean failing of an institution. It simply is failure to accomodate ones spouse and his family in your world of dreams and aspirations, its a personal failure indeed.