I don't think there is anything grammatically incorrect with your sentence, but it would sound more natural to use these sentences instead: I wish you would have had a happy Christmas. I wish you would have had a merry Christmas. I wish you had enjoyed yourself on/last Christmas.

"I wish you were happy" makes more sense. Now I'm wondering, Do you understand what "would have been" means? It's something like an imagined situation, the opposite of what actually happened. For example, "You would have been there." means I, as a speaker, wished you were there in the past but you weren't there in reality.