DvD. 3D is a horrible fad which needs to die. HD and Blue ray are overpriced for such a small improvement in picture quality and storage capacity... also there is a shortage of really good stuff on them. So I'll stick with my DvDs for the moment.
Blu ray all the way. Best hd experience. We have a good cheap store that rents out BR movies pretty cheap. DVD, that is obsolete now. Digital HD would be ok, but they always ruin it by charging premium prices to get maybe 720P. 3D is still gimmicky in my book.