What are bad games that are carried by good dlc/expansion packs?

I've been thinking about Neverwinter Nights 2 recently. The game is pretty controversial and is usually considered mediocre at best, especially the plot(which is crucial for an rpg). However it has an expansion pack named Mask of the Betrayer. This expansion received widespread praise and is considered by many players to have one of the best stories in the history of gaming, has a robust and complex non-linear gameplay and plot has a lot of meaningful choices. It's insane how it is even in the same game with the main campaign. Even today Mask of the Betrayer is often called the best dlc ever by people who played it.

Are there any examples of similar situations?