Blizzard's first foray into the first person shooter genre was a bold move for the studio best known for its strategy titles and its MMO, World of Warcraft. Blizzard is first to market with Overwatch, its entry into the nascent, but rapidly growing hero shooter and unfortunately for everyone else, Blizzard's managed to hit the ball out of the park on its first swing.
If you're both a fan of the MOBA genre and Blizzard's various properties, there's no reason you shouldn't check Heroes of the Storm out. It may seem like Blizzard's just got another "me too" on its hands at first glance, but there's enough to set this MOBA apart from the rest and it all combines together to make for a distinct and thoroughly fun experience that no fan of the genre should miss.
On a more personal level, Hearthstone is solid enough that if it gets its hooks in you, they will dig deep. The game takes on a Civilization-like level of addictiveness where instead of one more turn, you'll often tell yourself "just one more game". That one more game can quickly become five, or ten, or more depending on how much time you have to spend and I imagine this is going to only be amplified once the mobile versions of the game come online.