Peter opted to be crucified upside down as a sign of being unworthy of suffering the same death as the savior. While as far as biblical teaching, and theologically i disagree with a Catholicism, I too don't really see how they have been associated with Satanism.
The cross has been made into some monetary scheme. It has been publicized along with WWJD and things like that. Christ doesn't stand for monetary gain. Christ bled, and died on the cross, by our hands to be a median between us, and our creator. The bible says that we will be able to tell our brothers and sisters by the fruit of the spirit. NOT by whether we wear a cross, or pray a certain prayer. Jesus isn't a money plan, or a political figure. He is the one who came to save, and die by the hands he came to save.
As for what Christ should be remembered by.. If we simply remember Jesus by his teachings, by all standards, he would have been just another good guy, and prophet. Nothing profound. Nothing out of the ordinary. The gravity of the death of Jesus, is that in death, life is given. By his death, and his death alone, we are offered redemption. Paul says in Romans 4:25 "He was handed over to die because of our sins, and he was raised to life to make us right with God." Jesus' entire life was profound. But the death of Jesus, was the fulfillment of God's plan of grace.