It's like Pokemon with Satan!
While much attention now is being paid to the Persona and Digital Devil Saga sub-branches of Shin Megami Tensei, the main branch (being just the lable Shin Megami Tensei) has been largely overlooked in the states. This has largely been due to the main series never making its way over to America until SMT: Nocturne. But thankfully the good people at Atlus decided in the early 2000's to localize this gem of a game and though it only sold marginaly in the states it led to the cascade of new SMT spin offs in the states. And this occured because of the pure goodness this game delivered.
As mentioned in the title this game is strongly reminiscent of Pokemon in the way that the overall gameplay is dedicated to the collection and leveling up of demons (to be fair SMT started the monster capture and collection gameplay long before Pokemon.) Unlike the Persona spinoffs where you fight generic enemy demon's and then collect cards to summon different inner personas, the premise in SMT is every enemy you fight can be coaxed or fused and then made to be part of your team.