Well, i'm a born-again Christian and i wrestled with this issue when my mom was diagnosed with Amyotrophic Lateral Sclerosis (aka 'Lou Gehrig's Disease), which is a gruesome, absolutely terrible way to die - basically, it is a motor-neuron disease that destroys the nerves that control the muscles of the body, leaving the mind fully intact. You can't do anything - except watch yourself waste away, dying a little minute by minute. Death usually occurs within 5 years of being diagnosed (in my mom's case, it was just over 3 years, in November 1982 at the age of 53!)
She was given morphine suppositories, inserted in the rectum to eaze her suffering. I periodically talked to the Dr., and, on more than one occasion, wanted to ask him to increase the dosage so that she would lose consciousness and die peacefully. They only gave her a certain dosage so as to not impede any further her efforts to breathe (the person usually succumbs to asphyxiation due to not being able to breathe)
My mom, being a devote Christian, i'm sure would have not wished this and this partly kept me from asking the Dr. for assistance, but i wrestled with doing it i will admit.
As it was, mercifully, she lapsed into a coma like state and died in her sleep early the next morning. I thank the Lord it happened that way as she was deathly afraid of choking to death. God answered her prayer (and mine) and prevented it from happening that way!
Though she suffered emotionally, mentally (as i did as well) and physically, i can look back and honestly say my faith in the goodness of God was strengthened - even when i cried out to God in despair. Often, i would see her an emotional wreck, only to see her the next time with such a peace. Instead of it being a faith breaker, it was a faith builder and strengthened my belief in the God of the Bible being a faithful God, Who didn't promise us heaven on earth but did promise us eternity with Him where He would wipe away all tears and there would be no more sickness nor death - that's where my mom is, with her Lord & precious Saviour Jesus Christ!
That said, someone being artificially kept alive would be a different story - just as we should not "play God" when it comes to euthanasia, nor should we prolong life that isn't really there in the first place.