I kind of feel the same way about AFI that I feel about the Alkaline Trio, although a lesser extent. AFI had more than 1 good album, 1 ok album, and then total garbage before and after those two albums (especially after Crimson, the stuff after was particularly trash). Black Sails and Sing the Sorrow are the only two AFI albums I ever feel compelled to listen to any more. But I don't dislike their earlier stuff nor hate their later stuff as much as I do with the Alkaline Trio.
That is another good example. The drop off after Crimson, WTF.
I've been really disappointed with recent Black Rebel Motorcycle Club as well, but haven't given up yet.