This concept is applicable near universally: games, economics, computer parts, whatever. If the category exists, the things within it are almost certain to be roughly balanced.
For “quick and dirty” comparisons between two things, this concept is incredibly valuable to understand. When you just need to know roughly whether something’s worthwhile, you can save a lot of time by keeping the deep analysis for later.
Note: I highly recommend playing Alien Swarm: Reactive Drop instead of the base game Alien Swarm. It’s a fan-made upgrade that’s better in basically every way – and just like the original, it’s free!
Alien Swarm lets you choose from a roster of 8 characters spread across 4 distinct classes. There are 21 selectable weapons (25 in Reactive Drop) to equip as either a primary or secondary weapon, and 17 additional equipment choices for your third item. All up, that makes a lot of combinations possible, particularly when you have a full squad of 4 people – and RD even lets you go up to a squad size of 8!