It's really funny because a lot of people think that Digimon is a rip off of Pokémon which is totally wrong and as they say "ignorance is bliss". Just because of the word "Digimon" especially the 'mon' bit, people think that it is immediately a Pokémon rip-off. I happened to have had been one of those people. I refused to watch Digimon when it started because it sounded like a rip off of Pokémon and there was a cactus with boxing gloves on! %( I mean come on, a cactus with boxing gloves thats as stupid as an electric rodent. Anyway I gave it a chance when there was a gap after Pokémon finished (and my nephew loved Digimon so I reluctantly gave it a chance). I ended up loving Digimon as it was alarmingly more adult than Pokémon and they had what many people craved... continuity.
The Comparisions Digimon follows the story of eight children with their respective Digimon, each with distinctive personalities and traits, working together in heroic situations (many viewers form emotional attachment to the character - I love Gabumon and my girlfriend loves Gatomon) whereas Pokémon centres around three kids who catch and train Pokémon (no matter what I still love Onix & Vulpix). Digimon can speak English whereas Pokémon can only say their name (excluding Meowth & Slowking - also Lapras can mind link with humans as can Lugia & Mewtwo) And finally Digimon follows a storyline where the heroes battle evil continuously, learn about themselves and each other. We also learn about their families, hopes, fears and watch them fight for what is right while Pokémon goes along the same line as Digimon but to a lesser extent and rarely does Pokémon follow up stories from previous episodes.
So all in all, why can't a person still love Pokémon but also watch Digimon. You may be pleasantly surprised at how different Pokémon and Digimon really are. After all I watch them both (their on rival channels but Pokémon is on half an hour before Digimon... but Digimon is opposite Dragonball Z (what a dilemma!) ;-)