10 Big Leaps Between Video Game Sequels

10. Half-Life (1998) to Half-Life 2 (2004)

The original Half-Life is considered a milestone for first-person shooters. Its focus on narrative knocked down the boundaries of what was expected from the genre, creating the most immersive FPS up until that point.

Which is why it's incredible that Half-Life 2 put some things about the first game in stark contrast by innovating even further. It established more of the world for the series outside of the Black Mesa research facility, giving the franchise an edgier tone that was able to ask grander and more philosophical questions about evolution and fate. 

In fact, "grander" is a good catch-all term for what Half-Life 2 did. Instead of being a sci-fi corridor shooter, it allowed players to explore large, uninterrupted environments, go off the beaten path and, via a number of vehicles, traverse some really impressive (grimy) scenery. Of course, one huge improvement of over the original was the depth of gameplay content. The brand-new Havok physics engine made the game a sandbox in and of itself, and the likes of the game's gravity gun gave the players some incredibly fun tools to take full advantage of it.

It's pretty remarkable that both games have been in the conversation for the "best of all time", especially considering the leaps and bounds Half-Life 2 makes from its predecessor.