Heh, I'm not taking anything too seriously, don't worry.
I'm not sure what you're referring to with songs and Shakespeare, but here's why I will never make a deal with the devil, no matter how lucrative it seems (even if say, theoretically, he were to make me a GOOD offer, which is to say, an offer free of malice and somehow in and of itself "worth" pursuing, possibly because he wanted to warm up to me before making a later offer that WOULD harm me; again, this is theoretical because such a thing will never exist): the reason why I would say "No. I am not interested. Go away." is because I know why he is making me the deal in the first place. I know it is to my harm, and even if it weren't this is the person who KNOWINGLY turned his back on God and now seeks to take as much away from God and the people in God's Kingdom as possible... so on principal alone, I refuse to deal with him, because frankly I despise him and he is the one person I feel safe saying "I hope he suffers in agony in Hell, and the sooner the better."
Even apart from principal, the dude just wants bad things for us. There's ALWAYS an angle, a catch with him. So, knowing that, it becomes clear that a person is ALWAYS better off refusing any offers from Satan, no matter what.