It's partly the difference between words and images. What draws you to look at a magazine in a rack? Usually the cover pic. What do you remember after browsing it? Usually the content of the articles. Human brains respond to images and words differently.
Images are quick, fleeting, look here! Look there! kinda things. It is vital, or was in the past, to be able to take a scene in with a glance and know without thinking what there was to fight, eat, and mate with. After a glance, usually no more is needed, certainly no deep thought on what you're seeing.
Words are different. Words and language must be learned. Words demand thought. What do these mean? What is the intent of the writer/speaker? Do I agree? Words can be lies or truth, serious or trivial, fact or opinion, whereas images merely are.
So reading is going to be better for you mind than television, (providing you are reading something written for people your age, etc.). The medium is more conductive to thought, deeper thinking, requires focus and attention.
Games are more complicated, since they are as different from each other as they are from other media. Racing, fighting, shooting games (arcade games, basically) may improve your reflexes and hand eye coordination, but there is only so much hand-eye coordination one truely needs, and it is more important to be reflexive than to have reflexes (and I say this as one who often brags about my reflexs

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Games like Civ do require more thinking about the situation. It is images, but text rich images, moves require thought not reflex, etc. Is it better for your mind than reading Shakespeare, the Federalist papers, good sci-fi, etc.? Not in my opinion, but still useful, perhaps better than banal reading like people magazine or romance novels.
Of course, that's just about your mind. Not every thing you do must be building to your mind. How you choose to have fun is between you and your chiropracter.
Exercise is of course vital, moreso for some people (young, old, those with sedentary professions or slow metabolism) than others. If you are healthy with the level of exercise you have, than I don't see why any more is any better for you, it's all about enjoyment one way or the other at that point.
Studying, well, if you gotta, you gotta, flunking out of high school is a road to poverty, and flunking out of college is a waste of money. Studying on your own is well and good, but again, once past a certain level of being an informed citizen, it is value neutral; know more (about things not directly connected to your life) isn't better, though it can make some people feel better.
Character building, now that is paramount. Games can, possibly, provide interesting situations in which to test your values (should I be considered evil after employing the Baron, etc.), though in the end character will probably come from being tested, which only really occurs around other people, which is where time is best invested.