My number 7 favorite game of all time is: Marvel United.
Marvel United is a cooperative game designed around the heroes and villains of the Marvel Universe. I believe that there are two core sets readily available: Marvel United - which features members of the Avengers, and Marvel X-Men - which features members of the X-Men.
In Marvel United, players play cards from their hand to a row of cards called, "the storyline." After every third card is played to the row, a villain card is flipped from the top of the villain deck and its effects are applied. There are six locations arranged in a circle where your hero pawns (and the villain pawn) can move. Each location has a threat on it that must be resolved. There are also likely to be "people" tokens at these locations, some innocent bystanders that must be protected, and some criminals that must be apprehended.
Players have three core tasks: 1 - resolve the threats on locations, 2 - apprehend criminals, and 3 - rescue civilians. These are all separate from the ultimate task: defeat the super villain. Defeating the super villain is how you win the game, but you can't even damage the super villain until two of the three tasks listed above is completed. This requirement preserves the cinematic feel of the game, giving it a kind of story arc. This feeling is amplified by the fact that after you complete your first required task, villain cards are flipped up after every two cards are played to the storyline instead of every three.
One of the coolest innovations of Marvel United is the storyline. Players each have cards that show action icons for: movement (used to jump from location to location,) attack (used to apprehend criminals) and heroics (used to rescue innocent bystanders.) When you play a card to the storyline, you not only get to use the icons on the card that you just played, but also the previous hero card in the storyline. This means players are constantly discussing plans as they try to play the best cards for themselves and for the player whose turn follows them. This innovation makes Marvel United one of the most "cooperative" cooperative games that I have ever played.
Marvel United's brilliance doesn't end there. Every player gets to play a unique superhero. Every superhero has their own deck of custom cards. These cards all show the core three icons in various combinations. So, once you know how to play, trying out different heroes is easy. But, each hero deck also contains a few cards with special rules (explained in a text box on the cards) that are unique to that hero. These decks are very thematic, and you feel like you are playing Iron Man or Professor X when you play with their hero decks.
The different villains are the same. Each has a villain dashboard that lists the way the villain works and how the heroes win or lose the game. Each villain also has their own villain deck and a unique set of threat cards that are placed on the various locations. Oh, and locations all have special benefit powers to help the heroes, but these can't be accessed until the threat to the location is resolved.
Swapping out different villains greatly effects the difficulty of the game. Playing against different enemies with different heroes will give you a varied experience that can be as difficult or as easy as you want it to be. Locations are also variable. Your play area is made up of six of these, but you have many more and you can swap them out randomly.
Marvel United is all about modularity. The heroes and villains can be changed. The board locations can be changed, and yet even with all this variety setup is quick and easy. The game is easy to table and easy to play.
If Marvel United had any weakness it would be that the villains in the base set feel a bit lack luster. I would recommend getting the X-Men set first, and then if you like it, picking up the original base set to add the variety of new heroes. I said that Marvel United is all about modularity. Well, with that modularity comes variety. Marvel United is also all about variety.
There are over 100 heroes and about half that many villains currently available for the game. Sadly, most of these are not available in standard retail. Happily, the publisher has launched a Kickstarter every year since Marvel United's release offering new content and allowing backers to order previously released content. So, if you want to go down that rabbit hole (which I have,) you can.
For it's theme, modularity, variety, ease of play, cinematic feel, scalable difficulty and cooperative play innovations Marvel United scores high marks with me and lands as my number 7 favorite game of all time.