While it certainly wasn't the first of its genre, Overwatch managed to popularize the genre in a way that had never really happened before, and a great deal of the series' success comes down to its cast of playable heroes. Though Team Fortress 2's nine playable classes are distinct and memorable, each of Overwatch's original 21 heroes is truly iconic, both in terms of their visual design and their unique set of abilities. If it wasn't for its vibrant cast of characters, Overwatch probably wouldn't have been as hugely successful as it was, and games like Marvel Rivals would have a hard time finding their niche.