I agree with you. The other posters make sense when they suggest that maybe your siblings chipped in for the gift, and that is why they're all listed on the card. But the fact that none of them called you, sent a simple card or facebooked you leads me to believe that that's not the case (sorry if that hurts). I'm pretty certain you're not upset about whatever the gift was. You're upset about the fact that Dad (and possibly step mom) were the only ones to really think of you on your birthday. I'm sorry that happened to you! You might want to make it known that you'd like to be acknowledged on your birthday. Not by a gift, but by a simple phone call, text, or whatever. My MIL always says to us, in a joking way, "Don't forget my birthday! These things are important!" Only she's not really joking. And I've never looked at it as geez, she just wants a gift. She's just one of those people who tells other people what she wants, so that she won't be disappointed. I hope it works out better for you in the future!
Oh, and to sort of answer your question - just today I sent a birthday card to a childhood friend. I used to write "Love...." and list me, my husband, and our 2 kids. She has met my kids twice. She and my husband get along fine but don't know each other well. (they live in another state, so we never get together) A few years ago I just started writing my own name on her card. I mean, really, it's from ME!! Might as well just say it like it is.