One definition of the Antichrist is: one who denies or opposes Christ; specifically : a great antagonist expected to fill the world with wickedness but to be conquered forever by Christ at his second coming. I don't think the Pope denies or opposes Christ in any way. He leads a church that doesn't conform to what we believe as Lutherans - but I cannot, in my lifetime, remember a Pope who denied Christ. The Pope and priests of the church preach of the Incarnate love of Christ - His death, His resurrection, His ascension, His coming again.
As well, when I hear the word Antichrist, I always go back to the Signorelli painting. Since I first saw it, I have always thought it as such a powerful statement of all that is evil. In its simplicity, it makes a profound statement. We see one who not simply opposes or denies Christ, but is evil and manipulates those who are weak away from Christ.