Let me put it this way, the only similarities are that it's about kids having proxy battles with monsters and that the main theme is about the monsters.
Other than that, they are absolutely different. Pokemon is about kids catching many monsters and compete in tournaments, sort of.
Digimon is about kids having mostly 1 only monster as partner and trying to save the world from whatever threat you could imagine(real and digital) sorf of.
Another difference is that Pokemon storyline is what you could call -forever ongoing- while Digimon story lines are finite. This is mainly a market decision though ( i think).
