Bad grammar — one the things that bugs me.
Should have been Barck and me.
Michelle’s message to the prince and his intended was self-centered and sophomoric, but Michelle’s grammar in using “I” was fine.
The part of her message that was incorrect English was her mistaken usage of the adverb “Hopefully,” a common mistake in the past few decades.
The part of the sentence that reads “as happily married as Barack and I,” called for a predicate adjective in the nominative case and “I” is in the nominative case: What the sentence actually is in its full form is: “I hope you will be as happily married as Barak and I are happily married.”
One would be wrong to say “I hope you will be as happy as Barak and me are happy.” If she had said “I hope you are happy, LIKE Barak and me,” that would have been ok, because “like” is a preposition and takes words in the objective case, such a “me” and “him” and “them.”
In contrast, the word “as” is a subordinating conjunction and introduces a clause, not a prepositional phrase. Similarly, one should say “He is as tall as I [am tall],” not “He is as tall as me [am tall].”
To get back to “hopefully.” One correct way to have expressed what she meant would have been “I am hopeful that you will be as happily married,..... or just “I hope you’ll be as happily married....” Her beginning the sentence with a hanging “hopefully” usage is grammatically wrong. Here it’s an adverb having no verb to modify in any logical way.
"...as happy as Barack and I" is 100% correct. The implied full sentence would read...."as happy as Barack and I are happy".