The perennial, endless debate among, well, people, not just the beer geeks, is "what is good beer"? Personally, I think it's the one human question whose answer is absolutely relative: A "good" beer is one that you like.
My "favorite" beer, for example, is whatever I think will taste best with whatever I'm about to eat (I usually have beer with food.) And I know my tastebuds are mine and that they "lead" my palate and "good beer" brain in a particular direction. (And so I hereby bequeath my share of the world's IPA's to anyone who wants them, but I retain all rights to my share of the world's malty brown beers.)
Anyway, Charlie Papazian has been pondering the whole "good" beer quandry over at his blog and it's definitely worth taking a look. It's a multi-part series, and I think the most current entry is part six or seven. To find the beginning of his series, follow this link to the blog, and then look at the left side of the screen for links to the whole series. Enjoy!