Gaming can be anything from Facebook games and online games (i.e. World Of Warcraft) and video games in general. Gaming can also be role-playing games, like Dungeons and Dragons.
How much of it rules your life?
If you look back on your day, and see that gaming (or any other activity) takes up a large chunk of time, then you may have to cut back.
Or, if you set a daily goal (one that you have to work hard to achieve) and use gaming as a reward for a day's hard work, that can work too.
So, to answer the ultimate question of whether or not gaming is a waste of time is relevant to you and your situation. If gaming eats up 3-4 hours a night and you still haven't finished the first chapter of your book, it may be good to cease gaming until you've started down to road to achieving your dreams.