I first came across Asterix in the 1970's and I loved it. I have all the books up to Asterix and the Actress. In Australia where I live I read the books out of order - that is in the English release order and not the original French (Asterix and the Banquet for example was later than some of the others after it as was Asterix and the Normans and Asterix and the Chieftain's Shield). Having said that, I know that my mother saw Asterix and the Roman Agent and yet missed Asterix the Legionary - arguably the funniest of all the Asterix books.
I have also seen four movies - the animated Twelve Tasks of Asterix along with three more recent French language productions of Asterix and Obelix take on Caesar, Mission Cleopatra and Asterix and Obelix at the Olympic Games (done to support the 2008 Olympics in Beijing). There is a fourth that I am yet to see.
I do have three other publications, the book of the Twelve Tasks of Asterix, Asterix versus Caesar and The Idol of the the Gauls (a game book) - as well as an audio reading of Asterix and the Magic Carpet presently on cassette (I'll shift that to CD when I have time).