Chiming in a little late here, but Hedgefield pretty much nailed the entire thing. I don't work at a game dev anymore (still in the industry though), but from my time in the biz...
What do you like most about your job? Why? --- Making games is just fun. Having an idea and turning it into something that other people enjoy is amazing. Being in a group of creative people, either artists or game designers or engineers figuring out a problem is one of the best things you can do to make yourself WANT to be better at whatever it is you're doing. What do you like least about your job? Why? -- The hours, dear god the hours. I've heard mythical stories of places where the hours are good, but there was a time right before final submission on one project that we were working, no shit, 18 hour days. Not sure what your relationship situation is now (or will be), but hours like that absolutely put a strain on my marriage. It was physically and mentally exhausting to me, and basically being an absentee husband wasn't winning any favors with my wife. The pay also isn't terrific (but this isn't a gigantic deal). What advice would you give your 19 year old self? -- Whatever decision you make right now, don't worry, because it doesn't seal your future to one path. As long as you're learning from it, no amount of time pursuing something is "wasted" time. If you decide that you want to be a game dev, then go for it, but don't feel that the decision means you always have to be a game dev.
Final dumb note: It seems like you're stressed about this decision. Don't stress! This is your future, it should be exciting to you!