To be honest? The reason I liked Pokemon initially was because all my friends did. Everyone liked Pokemon back then, it was a nationwide craze...or at least a local area craze, but when you're a kid the entire world revolves around you; I never heard a single bad word about Pokemon when I was younger. Being eight or nine years old at the time, I was a happy little drone content to be a part of it; I didn't even stop to think about it, I just thought something along the lines of "Hey, this is really cool!" and went with it from there. The anime was exciting, the games were fun, and there was nothing quite like bragging about which cards you had. It was something I could share with my friends and it wasn't boring and, at the time, that was more than enough. Who really has a deep reason for doing things at that sort of age? It was all about being cool and not being excluded from social circles. We all banded together around Pokemon. I was no different from any other kid at that age.
These days, I suppose it's partly for nostalgia, and partly because the video games are one of the few constant things in my life: people say they've changed, but really the changes are window dressing and generation hopping: strip the mainstream games right down and they're all identical. They're still fun, in short.