Quite on the contrary: I am actually talking about Beamer. Maybe I was just extremely unlucky to only see really bad presentations, but I have not seen any beautiful presentation in Latex beamer and many great ones using Powerpoint or Keynote or some other tool.

I don't know what kinds of presentations you've seen, but I've seen (and made) more-than-decent presentations with it. Plus, if you have any math in your slides, neither PP nor Keynote hold a candle to LaTeX. That being said, I agree it is usually quicker to get fancy effects in either PP or Keynote.