Nope. Only some states allow Civil Unions or Domestic Partnerships, and the benefits/responsibilities for them differ from state to state. CA Domestic Partnerships (which I am in) are considerably different than Civil Unions offered in VT, and a far cry from Marriage offered in MS. Marriage-like arrangements of any kind between same-gendered people are against the law in VA.
The most notable difference is that any Federal benefit or right that specifies spouses is completely unavailable to gay couples in DPs/CUs. There are over 1100 of them. No arrangement made through a lawyer could possibly confer any of them on my partner and myself.
Thanks to CA’s Domestic Partership laws, I have hospital visitation rights and some inheritance rights that I would not have otherwise. An advance medical directive that gives my partner decision-making authority over me in the case I cannot due to medical reasons can be drafted by a lawyer that might stand legal challenge in court, but frequently they do not if a family member chooses to object. (Granted this sometimes happens to married folk, but not nearly as often.) Inheritance can also be handled to a certain degree through legal documents, though again, family challenges more often than not can break through any will or inheritance agreement, especially in more homophobic states. And adoption, a right easily granted to second parents in a fully-recognized heterosexual marriage is something that is often denied to second parents in a domestic partnership, civil union, or other available marriage-like arrangement.
A final point, though. A marriage license costs something in the neighborhood of $100, does it not? To get all possible legal arrangements, which would fall far short of the protections and priveleges of actual marriage, would run my partner and I about $2500.
So, unequivacably they are not sufficient. If the Feds decide to start recognizing Civil Unions or Domestic Partnerships on equal footing to Civil Marriage, we might get somewhere. But I don’t see that happening any time soon.
I’m sure more people will post, but if you want any more detail, I’d be happy to dig it up.