So, I've heard that the old rivalry between the two shows, Pokémon and Digimon has resurfaced. This has most to do with things like Black Kyurem/White Kyurem and the Mega Evolutions reminding people of Digimon.
So fanboys are arguing that which one is ripping each other off. Ripping off what exactly? Both shows are about kids in a strange world where inhabitants are monsters that become bigger and stronger in a process (incorrectly) called "evolution". Otherwise, the shows are like day and night.
Note that in most continuities of the Pokémon series, there is one world where humans and Pokémon coexist. In Digimon, the titular monsters live in a realm created by human computers and somehow, a small group of human kids get into that world. A major plot point is travelling between Digital World and Tokyo City.
There are an exact number of Pokémon that rises by around a hundred every three years. Currently (2013), its 718. All Pokémon are listed in the Pokédex, a Pokémon encyclopedia that gives us a bit explanation over several things. Meanwhile, Digimon is not nearly as consistent about that - each series has their own set of 'mons and some sets overlap in inconsistent ways.
Oh, and the series have completely separate origins. Pokémon started out as an unusual RPG idea by Satoshi Tajiri known as Capsule Monsters. Digimon was made when some guys at Bandai figured that Tamagotchis seem to be rather unpopular among boys and sought out to fix this. Then it was made an anime and a card game out of the stuff, and the rising fandoms met each other, and it was not pretty.
Oh, and SABO LIVES!!!!!!! YAYYAYYAYYAYYAYYAYYAYYAY... I wonder what this leads to.