Don't worry, it's not about how ugly the new ones are! I posted this as a response to a topic about the generations on an unrelated forum, but I thought I'd bring it here, too:
Keeping in mind that things are different as a child and as an adult, there seemed to be so many more secrets and spending hours trying to uncover them was worth it. An evening spent scouring the Internet for clues on how to find that mythical Mew or for new hearsay paid off when we all discussed it on the playground the next day, thinking we were one step further. There weren't nearly as many guides, videos, official statements, etc, that could solve the puzzles or truly debunk the rumors, though we may have just been inefficient children and didn't find them.
With the coming of EVs, natures, breeding, and egg moves individual Pokemon became easily disposable. When all Blastoise were created equal but for a few stat differences, putting weeks of work into leveling one the old-fashioned way was something to be proud of. Now the trophies are things like shinies - legit or not - or Pokemon you've tediously bred through generations of discarded parents and grandparents for perfect numbers.
Modern Pokemon probably appeals more to battlers now that it has a more complex system for that, as well as people who want to collect. I was an adventurer and a social player, and there's precious little uncharted territory left and too few people to explore it with at my age.
I'm curious what everyone else thinks, especially others who've been with Pokemon since its introduction. Was the atmosphere surrounding the games different during gen 1? Was it better or worse? Was there more mystery or more opportunity and motivation to play with other people?
If you're curious about the "old fart" thing, I'm in my early twenties now.