I don't think there are 6 LCD games that I actually like for LCD specifically..most of them are bad. That being said R&M and Alien should be in everybody's list as they are really the best when it comes to LCD usage / theme integration - even if you don't care for the gameplay or themes themselves.
Can't speek to Halloween or Ult at this point but I haven't really liked what I've seen of Halloween so far.
All the Stern LCD's seem pretty generic, but Stranger Things seemed okay. Haven't played most of the JJP games, but they seem to do a better job overall than most (although they are all getting better). Sadly though, I really don't like any of the Stern LCD games - LCD or not. At least not at 7-11k worth. Godzilla mechs look cool, but hate the art and most likely the LCD as well (not sure yet).