Mr Light wrote:
The first season is absolutely wonderful and introduced a fascinating mythology. The second season was almost as good. The third season immediately went to crap. The fourth season's back half managed to save the show a great deal. The fifth season was horrible and Alias: The Next Generation. So basically just get the first two years and you'll get the good stuff.
Absolutely agree. I watched S5 mainly just to "complete" the series, but if it had ended at season four I would have been satisfied.