I like orgo and g chem, but as a Chem major, I'm a bit biased.
Keep in mind that there are MANY doctors out there that hated every last one of these subjects, but they knew what they had to do to get to where they are and do what they (hopefully) love to do. I don't think whether you hate or love these subjects or find them extremely easy or hard has much to do with how good of a doctor you'll be. It's just how determined you are to make it. There are things you'll love, and things you'll hate, and some of those things won't have to do with science at all. Then again, if you're mostly based in research, it may have some bearing. I was thinking more along the clinical side of medicine, though.