There are some Mario titles that are fundamentally different than its predecessors. Some of them are fundamentally the same. The reason for this is because there are a lot of people who ask for the same stuff, and people who ask for different things as well. Luigi's Mansion was definitely one of those titles that has Mario & Luigi in it, but is completely different than what Nintendo has done before. I'm not sure about the horror aspect, but in terms of the gameplay itself, it bore no resemblance to their previous titles. Paper Mario was another attempt at going for the RPG in the Mario series. Changing genres is a big thing to do, and instead of Princess Peach getting kidnapped and you go through multiple worlds to save her, Paper Mario adds some twists here and there and gives the characters scripts and personalities.
