Original: Mario Bros.
Sequels truly don't get any better than Super Mario Bros., but a lot of people reading this might not even remember the original Mario Bros. It was an arcadey platformer in which Mario and Luigi had to avoid and defeat turtles that popped out of pipes on single-screen levels.
That made more sense for a plumber—he was eliminating the pests clogging the pipes—than the galaxy-spanning adventures Mario has these days, but Mario Bros. was still inferior to what would directly follow it. With Super Mario Bros., Nintendo and Shigeru Miyamoto didn't just create a sequel. They reinvented a genre and provided the industry with a true kick in the ass, not to mention the most influential game ever created and one of the most beloved legacies across all mediums and cultures.
Without that transformation the game industry would not be what it is today. See? Sometimes change is a good thing.