Of course they're comparable. They are both serotonergic psychedelics, which produce typical classic psychedelia. It would be difficult to compare 2C-B to Salvia, sure, but 2C-B to shrooms (or psilocin) is a completely valid comparison if you are looking for relative intensities at particular doses.
@gymstud, I can't provide you with exact doses, since my 2C-B came in pill form. However, I can tell you that you can indeed judge relative intensities from phenethylamines to tryptamines (and lysergamides), and given the Erowid dose chart for 2C-B, you would be looking at a strong shroom dose to match a 36mg 2C-B trip.
Having said that, I would advise you to start with a reasonable shroom dose. As you know, every compound is experientially different, so you will want to get to know the compound in a friendly way before going balls deep. 20 wet grams (equivalent to 2 dry grams) of psilocybe cubensis is an intense experience for me, so I would recommend starting off at that dose. I may be slightly sensitive, as others seem to recommend slightly higher, but that is my recommendation. You can always take more next time one you're familiar with how that dose affects you.
I hope you enjoy your trip is you do partake!