So here is the question: How do you want to go about saving the world? I have written before about Sentinels of the Multiverse, a cooperative superhero themed game, and just this week I got to try Legendary, a quite different cooperative superhero themed game. Stacking them up against one another is an interesting exercise as they have some obvious similarities in theme but the mechanics are totally different.
Lorewise there is no comparison. Sentinels is the clear winner because when you play in Sentinels you are a specific hero and have all of their specific cards and abilities. Your deck plays very differently depending on who you are playing and your cards have a lot of great thematic elements, quotes, and good mechanical support for the theme. In Legendary it isn't even clear what you are because you draft hero powers and SHIELD recruiters, and add them to your basic SHIELD dorks to make a deck. While some heroes have themes they aren't nearly so differentiated as they could be and it feels weird to be some kind of a SHIELD / Storm / Spiderman / Hulk hybrid. I don't even know what I am meant to be, and that seems like a baseline you want to hit!
Legendary feels more balanced than Sentinels but that balance comes at the cost of differentiation. The super villains have almost nothing making them feel different and because the heroes get all mixed up in your deck the game is very similar no matter what you pick. The heroes are better balanced, the villains are better balanced, and I don't really care that much that they are because the game just isn't as much fun.
Normally I am the person desperately hunting for razor's edge balance in games and tweaking my games until they have it. In Sentinels I spent a ton of time trying to figure out ways to balance the heroes and make the rubbish ones more competitive but I don't care that much about doing that in Legendary because it feels like it lacks replay value and engagement. I know I could improve the game but just don't care to.
This is another great example of how balance is a good thing (Sentinels would be better if the balance of the heroes wasn't so completely out of whack) but it is far more important that the game grab you and feel fun that it is to get the numbers right. You can do both though, and you should!
I think Legendary is trying to ride on the fact that it has the actual IP behind it instead of the made up superheroes of Sentinels and that pushed out a game that was just not up to snuff. Unfortunate, but definitely unsurprising. Games with IP behind them go that way most of the time I find.