I've played every generation apart from the current Black and White generation. The only development seems to be that there's a few new Pokémon, there seems to be no gameplay changes so I've considered that maybe they aren't even worth playing. I can name none of the new Pokémon since Diamond and Pearl apart from the legendaries and the starters, and can otherwise name 493 which I think is quite an achievement and should serve as some kind of threshold.
To me Diamond and Pearl seemed a bit silly. They'd ran out of coherent solutions which made certain Pokémon regional and thus stopped any the usefulness of any kind of cross-regional movement. When they released Heartgold and Soulsilver they were entirely for flavour, there were no Pokémon you couldn't encounter in Diamond and Pearl.
Lumping all the Pokémon in Sinnoh seemed farfetched to me, and I suspect they've done something similar having lumped them all in Isshu, available by some kind of device you get at the end of the game. To me the fact that you can catch all the Pokémon in one place seems to be symptomatic of the fact that the games have become pretty ridiculous, not that Pokémon has died per se but that the series in general doesn't feel as original and adventure-orientated as it did. It also shows perhaps that Pokémon has moved on, and that all the old Pokémon are just novelties, things they're forced to include but that are forgotten by the current generation of players.
What about you? Is your Pokémon history numbered, or have you played everything there is?