Katz's The Third Magic was an interesting one, I remember. The Publisher's Weekly description spoils an unnecessary amount of the plot - I seem to recall being a decent way into the book before I realized that the alien portal world was Arthurian, and much, much further before I realized the degree to which Katz was inverting the typical Mary Sue paradigm.
The line "Poor Mordred. It's not really your fault either, is it?" (or words to that effect) still strikes me as a brilliantly chilling next-to-concluding sentence.

But bad wish fulfillment fantasies? I can't recall that many of them, to be honest. I think I just closed a lot of books that bored me.