Collectible Card Games (CCGs) is a game genre that goes way back to Pokemon and Magic The Gathering (MTG) board games which were played with physical cards. After the explosion of the Battle Royale genre on Mobile, Card Games (CCGs) are now trending. We have Hearthstone, Shadowverse, Yu-Gi-Oh, Eternal, Elder Scrolls Legends, Epic Card Game, Mythgard, Marvel Duel (full release pending), Legends of Runeterra (full release pending) and Gwent (full release pending) to name a few.
The game that started it all
Blizzard was the company to popularize CCGs in the mobile market with Hearthstone. Magic the Gathering had released on the play store prior to HS and so did other CCGs from the east.
Hearthstone was the game that exploded though, with a potential player base of 10,000,000 players at its peak. Having the Warcraft universe to lean on, probably did the game wonders.
Perfectly suited for mobile
CCGs are the perfect game models for mobile, both for the player as well as the developer. The player gets a slow-paced game that they can dive into for quick matches. They can even pause a match against bots and pick it back up later. The developers get to monetize the game with a free-to-play and pay-to-progress (players build their collections) model. While this can make the overall experience pay-to-win, many developers take steps to prevent the same. Developers like CDPR and Riot games have proved that a CCG can exist without being pay-to-win.
Replay-ability over 9000
CCGs provide tactical depth, both for the average casual player and for hardened veterans. They usually contain multiple modes such as constructed (playing with a deck from your collection) or draft (create a deck from a random set of choices). Additionally, many of them feature story campaigns relating to the lore of the game world. These games play out against the AI which helps in teaching newcomers the mechanics of the game. It also lets them connect to the lore of the game-world which can be important to some players.
Coupling this with the myriad of decks that can be built in each game, you have endless replay-ability. On the competitive side, things can get narrow since certain cards will always be more consistent but casual modes exist for those who want to have fun.
I have probably spent thousands of hours in various mobile card games (CCGs) and I look forward to spending many more with the mobile releases of Gwent and Legends of Runeterra.