Video games set expectations. However, this isn't just in advertising and previews, but in playing the game itself. From beginning to end, games are a package deal. The title and menu screens can set tone, while the initial tutorials and levels give the player an idea of what's to come.
Any game (or movie, series, etc.) can have an excellent premise and brilliant execution. But, all games need to end. The early days of the arcade provided titles that were technically "endless" that continued to grow in difficulty until the player ran out of quarters. Since then, the industry has evolved, developing games with plots that have conclusions. There are exceptions like Massively Multiplayer Online titles, which depend on the continual addition of content to prolong their lives. However, most games have a clear-cut ending, be it a final resolution or an open-ended cliffhanger.
