Doki Doki Panic easily. It was an actual new game and it felt like a new adventure. Also being able to play one of four unique characters was a great feature that really made the game stand out. It was tons of fun and is an eternal classic of a game. Videogamedunkey rates it as the best game of the year every year.
The Lost Levels kind of feels like a troll game. Calling it an expansion of the first game is being kind. The game is hard in unfair ways. Not cool man.