My parent's issue with the game is that the child isn't advancing mentally, but degradating. With all due respect, I wouldn't want to see my sister end up with a brainless job living a dead life.
Of course not, but most people will, and indeed, if you want your sister to have a big TV and all that other stuff, other people will be doing those jobs that you think are beneath her. But, that is nothing but a game. All people who work are in brainless jobs, unless they are one of the very few that get the rich rewards, you're basically trying that game and losing it. Drawing's not going to help her.
Get your sister to try this experiment, print off the alleged proof of the poincare conjecture by Grisha Perelman and say "Hey Ma, Pa, I'm having a problem with this, I think this bit here on page 53 is wrong, what do you think?". The blank look on their faces should satisfy her that playing the computer game isn't going to damage what isn't there in the first place

Neither will it do any harm to the bits that are there. Rinse and repeat with some other subject if you like.
Working with computers is a job that supposedly helps the world so therefore it is usefull.
Oh please, do you get your moral ideas from watching Lizzie Mcguire or something?

Computer games on the otherhand are not usefull in large quantities. My sister can draw, a skill that I consecrate and gretly respect due to it's beauty. My sister abandoned drawing, largely because of lack of interest, but guess why the interest waned. The computer games completely left her with literally no time for anything else.
What could your parents do? What did they give up in order to do whatever they do
now? Do you think having kids is therefore bad?
For me, 2 years of saying "Goo goo gaa gaa" that increased my intelligence no end I can tell you. So did sitting through bambi and the jungle book. I've even been known to visit a park and kick a football around - a well known activity of the intellectual. Teaching someone to count to 10, that was a high point in my parental career - something that compared well with reading that book on Galois theory a few years before.
I can't wait for the teenage years either, there's no doubt in my mind the last 30 years I've spent researching have really been to work up to that climax where I get to converse with a group of teenagers again and I once again experience true genius, and pay for it to sit around the house. Yes, if destroying computer games is necessary to get that, why are we even having the debate?....think of the children!! I've just thrown the playstation in the bin

It certainly seems to share a lot of the things you believe computer games have that make it bad (a) It's addictive (b) It requires no intelligence, worms can do it (c) it's violent and, unlike computer games, that's real pain and real blood.
(d) It takes a lot of time away from doing things like drawing or solving the energy crisis or whatever else you fancy you might have done if only it weren't for the pesky kids [Who didn't turn out to be Mozart either, the blighters and now worst of all, they're playing computer games! I thought buying the computer would make them more cleverer than what I was, I guess in a way by being that dumb I've given them that chance]
(e) It often involves a heap of activities that by themselves are considered 'brainless jobs', cooking, cleaning, putting passwords on computer games and so on
(f) It's expensive. Which might mean rather than drawing or playing the piano or whatever activity expands your mind means working on a job that is anything but educational or vocational to get enough money to clothe, feed them and buy them computers [why though? I can't think of any reason to give a child a computer other than games - except the ones that someone is now going to type, which should give us a laugh

]
(g) It requires that you sleep with the opposite sex, which I include merely because that might reduce the chances of you being a good pianist by at least 50% [Not entirely sure about that one, see Horowitz for more details]