I learned that the real reason Pokemon got popular while Digimon didn't: Marketing.
[spoiler=Explanation]For Pokemon (way back then), the anime was on Kids WB, which had a line-up of awesome shows for kids, the merchandise was marketed for everyone, and the games were on the Gameboy, which was more accessible for kids.
While, for Digimon, the anime was on Fox Kids, which, now that I think about it, had a slightly lackluster set of shows that were more aimed for kids, the anime was edited to try to be comparable to Pokemon (which made it seem like a crappy clone), the merchandise was mostly action figures, thus mostly for boys, and the games were on the Playstation, which was more for serious gamers.[/spoiler]