I'd think that, honestly, the only thing everyone would agree on is that if there's no procedural generation whatsoever, it's not a roguelike. (Of course, I'm probably wrong about that, and there's someone out there who doesn't think that's an important factor.)
Permadeath (or at least permanent consequences for death) is a pretty big one for most people too, though probably not as unanimous.
For me, turn-based is important, too. I think that'd be the main thing for me that spells the difference between a "roguelike" and a "roguelikelike."
Honestly, though genre definitions don't really matter that much to me, a good game is a good game.