Half of the levels are neat as fuck, half are fucking terrible. The entire game is bogged down with repetitive animations and sequences that take far too long. Watching characters unlock after a level is completed, for example, is infuriatingly long-winded. Characters like Spider-Man and Iron Man are completely unplayable because every time you try to switch characters, you will instead switch to useless-ass Peter Parker and Tony Stark (also a problem in
Lego Marvel's Avengers). In levels where you have the Hulk, if left as an NPC, he'll almost always change back to Bruce Banner, and you'll have to change back and watch the long animation play out again. If you die as Iron Man or the Hulk, you will respawn as Tony Stark or Bruce Banner, and have to watch the transformation sequence again.
Combat has been changed so enemies take way too many hits to kill. They made combat take longer; they didn't make it more fun.
This is a post-
Lego Batman 2: DC Super Heroes LEGO game, so the open world is full of collectibles. The problem is that they all stay on your map even after you collect them, making the map a clusterfuck. Even worse is the newspaper comic filter they put over the map, which makes it even harder to see.
The overworld contains races, some of which require a boat. However, the only boat you can unlock in the game requires you to find all five "vista points" in the open world, to which they give you no hints. It's maddening.
This would have been a great game if it had been made in 2013. The levels and ideas are more interesting than the original
Lego Marvel Super Heroes, but the game itself is worse. The voice acting is terrible*, and almost every single thing was changed not to be more interesting or challenging, but simply to take longer.
HOWEVER, in spite of what I said, I appreciated a lot of things about this game. The side quests and alternate versions of characters were great, and like half of the levels were good. I don't know.
Addendum: After playing
Lego DC Super-Villains, I can confidently say that that game is a far superior vision of what this game was trying to accomplish. Transformations are quicker and don't need to be done every time you die. Collectibles are removed from the map when you collect them. Even the nebulous challenges (like the vistas one above) have actual hints telling you where to find them. It still has a lot of the problems these games have (like long camera pans you can't skip to over-explain your objective in a level), but it's a much, much better end product due to learning from LEGO Marvel Superheroes 2's mistakes.