Well...Digimon never quite caught on like Pokemon. Here's my theory on why it's so heated with Pokemon.
Gen 1 is basically a "retro" property now. It is to some fans what the original Power Rangers or the 80's TMNT show were to their fans. Though successors have surpassed them in quality, the fans are actually quite dismissive of the property and hold on to the idea that the original is the only good one.
Gen 2 is the Mega Man 2 of Pokemon. It was the follow up that took the original and improved on it in every conceivable way. This MASSIVE leap in quality left an amazing impression on some fans, who to this day admire GSC for its achievement and don't feel like sequels have really matched Gen 2 in magnitude.
Gens 3 and 4 are very divisive gens. Hardcore players love them for what they brought to the metagame. In 3's case, it's probably hated more by "genwunners" for being completely unrelated to Gen 1, while Gen 2 fans think it was a weak upgrade, or maybe even a downgrade in several areas, compared to Gen 2.
Gen 5 I honestly haven't been around long enough to gauge, but I would assume it's also quite divisive because of it's "soft reboot" atmosphere. Long time players may love the breath of fresh air, or hate the disconnect.
By comparison, Digimon doesn't have the "retro" stigma, despite being roughly as old as Pokemon. This allows it to be judged more fairly. In addition, Digimon was a tv show with a clearly defined plot and characters. Pokemon has always been a blank slate for the player to use as escapist fun. So, being less "engaging" than a video game, people grow less irrationaly attached.
We are awful, we are probably one of the worst fanbases in the world, every time someone discussions a season/ game gen we all scream like five year olds. That's why I hang around the BW2 boards rather than here.
And don't even get me started with competitive play arguments
Gamefaqs in a nutshell (http://error1355.com/img/gif/gamefaqscant.gif)