I think some of the reactions are somewhat harsh. Maybe mom's email was wonderful because it was unexpected. If mom never calls, or writes on his birthday, perhaps it extra special to hear from her. Yes, he was underappreciative of your effort, but perhaps he didn't recognize how special it was....he had dinner, time with kids and a bath. He probably has dinner most nights, sees the kids, and has the occasional bath; it probably didn't occur to him all the effort that was involved for a lovely, but fairly ordinary birthday.
Let him know how you feel. It will make you feel better, but don't be surprised if he is completely clueless.