i rarely buy modules (preferring to make my own adventures), but i would be much more likely to buy a dungeon crawl than, say, a mystery adventure or something more combat-lite.
i also don't care for horror or Cthulhu-esque stuff in my fantasy, so i'd bypass anything with those elements in it.
"ancient mysteries" i would also tend to avoid, as they usually make assumptions about how your campaign world works. anything that's not generic enough for me to plug into my homebrew world wouldn't get used.