If you just play through the game going through the different worlds to try and complete the storyline, the game isn't too long though not too short either. However there is quite a nice amount of side content to engage in. There are some side missions you can get from talking to people in the hub world before each mission however these usually only consists of finding particular items which you'll come across when playing through the game normally. Instead the main bulk of side content come from things like simulator discs which are extra missions you can find while playing through the game which lets you play through an instance of each heroes past. There's also a lot of concept art and trivia to collect, not to mention that the game can warrant several playthroughs due to the large amount of characters available, these include famous characters like Deadpool, Daredevil, Spiderman, Iron Man and The Fantastic Four (each member being it's own character of course). And some more obscure characters like Moon Knight, Blade and Spider Woman along with a lot more. A lot of the characters are also unlocked as the game progresses as well as some requiring you to complete certain side tasks to get them such as in the case of Silver Surfer (requires you to complete all the simulator disc missions) or Daredevil and Black Panther (Requires you to find a certain amount of "medals" hidden through the different levels). You can also purchase some characters as DLC like Hulk and Nightcrawler, it even includes some of the villain characters such as Magneto and Dr. Doom himself. There's also different costumes that can be unlocked such as the Classic Wolverine costume or Symbiote Spiderman, which besides changing the appearance of the character also offer different bonuses. So safe to say the game will keep you busy for a while.