There's been a long running, sometimes venomous debate as to the relative merits of science fiction versus fantasy. The discussion dates back to the letters pages of Weird Tales and Astonishing SF during the pulp era, so one would assume there's something to it; something meaty to fire up the century-long flamewar.
You'd be wrong.
SF and fantasy are buttonholed into discrete genres, and it's a mug's game. It's a nonsensical definition between make-believe settings utilizing make-believe powers in some way that has a measurable impact on the plot or characters of the work. it reminds me of the bickering between the deeply religious and the coldly scientific among the legions of talking heads.
What the speculative fiction genre (a much better descriptor) does is put characters in situations against a background divorced from our daily reality. That helps to highlight the characters and their motivations, in my mind at least. I'm sure others could argue.
Good speculative fiction is immensely satisfying. Moby Dick. Rendezvous with Rama. The House on the Borderlands. The Road. The Shadow of the Torturer. The list goes on and on. Readers, please avoid limiting your book consumption to just one of these two "genres" - if you do that you'll miss out on half the buffet of wonderful literature before you. If you gravitate toward one end of the spectrum, step back and choose somethiing outside your comfort zone. Explore.
Do read with discernment, though. There's a lot of utter crap burying genre fiction shelves, which is due to a whole host of problems, some of which I may go into in the future. If a book does nothing for you, put it down. Leave a bad review. Warn your children. If it's good, do the opposite. Blog it, talk it up, leave reviews.
Get out there and read.