As I said, Lufia 2 had the evolving monster thing long before Digimon and Pokemon did. Does that mean that Digimon, Pokemon and Keitai Denjū Telefang are ripoffs of Lufia 2's monster raising system? No.
Evolution is basically a way to represent growth and in a tamagotchi type thing in is natural that you would see a form of growth, actually it is pretty much a standard. The thing that set digimon apart was the ability to fight other digimon. They basically made a manga series then an anime series based on the digimon tamagotchi things. The creator of Pokemon also wanted the Pokemon to grow so he used evolution as the term used for growth. I mean seriously, Pokemon was originally based on the idea of bug catching, look it up.
As was previously stated the "mon" means Monster. With the evolving creatures thing coming from an entirely separate backgrounds and the "mon" thing just meaning Monster it is obvious that Digimon's history is not at all connected to that of pokemon.