I'm another who likes Dungeon. The very basic reason as to why is because I really don't like being forced to use the stylus, and since that's what Ranger uses, I don't like playing.
The other reason is the storyline. Not just the fact that a human turns into a Pokemon, but everything else. I cried while playing Mystery Dungeon Red (it's the only one I've gotten far enough in to say that), and Time/Darkness just grabs me. It's a refreshing change from the other plots in Pokemon games.