Definitely want to echo the irony of asking a pre med forum this question. Putting aside respect for a moment, lets talk about difficulty. I agree that there are some joke PhDs available at that (cough, online DNP degree, cough). However, I think that the difficulty of obtaining a PhD from a good program and producing a good thesis will definitely be harder than medical school. Creating is way harder than learning. After finishing up my undergrad "thesis" as my school likes to tote it, I have so much more respect than I already had for my professor and the others that I worked closely with. It just showed me how little I know about the scope of my topic, and at how low a level I perform than they do. Granted, lots of that is from experience and volumes of literature absorbed, but still I felt like a five year old in a room of doting parents when I gave my thesis defense. The data I collected will be published, but I would be shocked (though flattered) if it reads much like my thesis did when my professor submits it. So please guys, have respect for our contemporaries and the far greater scope (and equal importance) of their research. More than a few PhD's are going to be teaching you during med school I would bet.
As far as respect goes, I would guess that the average physician probably gets more respect than the average PhD simply because physicians tend to be more common in public experience, and their effect is directly perceived.