Some people do have photographic memories (like this Korean artist can draw things after seeing them:
http://www.kimjunggi.net/bio/). From a biological perspective, things are easier to recall when you either 1. attach meaning to them, or 2. when you have regular exposure. This is because memories that are easier to recall have more neural connections to that particular memory (someone posted an article on language learning recently, that mentions this..I'll have to remember it). You make more neural connections, or strengthen current ones, by repeated use. If I recall correctly (he he), emotionally charged memories are stored by the hippocampus, and are easier to recall. The sense of smell is close to the hippocampus, that's why your memories of smells are so strong.
As for me, it takes
forever for me to memorize something. What I can do is quiz myself and give myself a "stressful" situation. Trying to remember something forces my brain to consider that particular knowledge important, because I'm trying to recall it, and it will shift to remembering that knowledge. Tests and exams in school are not (ideally) to find out how much you know, but to cement what knowledge you already have. This is why SRS works: you're being quizzed, and you're exposed to the knowledge with some regular basis.