I enjoy match-3 games, and this comes with all of the benefits and drawbacks that come with competitive versions. (Matches aren't timed, but opponents take alternating turns against you, with possibilities for long strings of watching the computer play when it gets a lucky combo.) The game makes full use of 4- and 5-matches, giving each a different bonus, and recognizing T-shaped and L-shaped 5-matches. (Games that don't do this drive me crazy.)
As a free-to-play game, I like that everything in-game is still accessible without purchase. Progression is a bit slower, of course, but it is possible to win "hero points" (in-game gold) and expand the slots available for heroes.
The unique elements of this game are two-fold:
1) A collectable card-game like element of choosing which heroes to keep and level up, and which combinations to use in each battle.
2) A chance for gamers not already steeped in superhero lore to get to know Marvel characters and interactions a bit better. It's quickly turning me into a fan!
There are two modes of play: "story mode" and "versus".
* Story mode has in-character intro and outro dialog, pulling you into a comic storyline. It's a fun way to immerse yourself in the lore of the Marvel universe.
* Versus mode pits your selection of heroes against heroes from another player's roster. It is worth noting that you are not actually playing the other person, but rather the AI using their heroes and abilities. This is a huge positive for me, because I don't have to deal with connection lags, people who afk for long periods, or trolling in a chat window. But if you're looking to match wits against a human opponent, this might leaving you wanting for more.
Over 40 hours in, this continues to be a deeply engaging game!