According to the Book of Concord, the office of the papacy is the Anti-Christ. At the time of the Reformation, the Pope had his fingers in all the pies in the world, doling out land to rulers, deposing rulers, and the like. Setting up a secular empire is not what the Church is supposed to be doing; hence, the supposed "Vicar of Christ" was acting in an un-Christ-like manner. That is more or less the definition of the Anti-Christ according to 2 Thessalonians 2:4.
The abuses have been greatly diminished since the Reformation. However, today the Pope still has the power to speak ex cathedra and establish new doctrines, which is still "oppos[ing] and exalt[ing] himself against every so-called god or object of worship, so that he takes his seat in the temple of God, proclaiming himself to be God" (2 Thessalonians 2:4). In this sense, the office of the Pope is still the Anti-Christ.
However, I see a distinction between the office and the man. The man in the office can behave in a way more fitting of the medieval popes who "lived it up" or in a way fitting of a spiritual leader. If the man's life and words are a poor example, I'm not going to pay him all that much attention; he's living up to the office of Anti-Christ. However, if the man's life and words are a good example, then I don't see a problem with appreciating the good he has done. I still wouldn't call him "my bishop," though.
Long story short, as long as the Pope can establish new doctrines on a whim, the Office of Pope is the Anti-Christ; the man doesn't necessarily have to be. I'm not sure how doctrinally-correct that is, but there you go.