All your favorite Marvel heroes are ready and waiting in the new Avengers Alliance 2 game, so I hope you didn't spend a lot of money playing the first one. That game is old news, and it doesn't look as pretty as the new one. This game was out in geo-limited beta a few weeks ago, but now it's available to everyone.
Like the original game, Avengers Alliance 2 is an action combat title based mostly on 3v3 combat. You build your team of heroes, learn new skills, level up, and generally beat up the bad guys. The visuals have gotten an overhaul in the sequel as well. Interestingly, I'm not immediately seeing any of the characters currently licensed to Fox. They were in the last game, so maybe they're lurking in there someplace.
This is a free-to-play game, so you'll have the option of spending as much as $100 on a single in-app purchase. You probably shouldn't do that, though. Avengers Alliance 2 offers various daily rewards and tournaments to earn free loot if you don't want to spend money. The first game was really popular, so I expect this one will be too.