Monster Squad is described as 'Lead your monster squad through islands all while battling exotic creatures along the way'. There are nine alternatives to Monster Squad for a variety of platforms, including Android, iPhone, Android Tablet, iPad and Kindle Fire. The best alternative is Final Fantasy III. It's not free, so if you're looking for a free alternative, you could try KINGDOM HEARTS Union X or Million Arthur. Other great apps like Monster Squad are Neo Monsters (Paid), EvoCreo (Freemium), Brave Frontier (Freemium) and Monster Park (Freemium).
Final Fantasy III is a 3d remake of the original of the same name for the Famicom Entertainment System (a.k.a. Nintendo Entertainment System). Originally it was not released in North America. Eventually it was re-made into a 3d version for the Nintendo DS.