i still have all of my pokemon, red, blue, yellow, silver, sapphire, ruby and leaf green. and am planning to get diamond and pearl both next month.
i remember playing blue when it first came out and thought it was really really awesome. after that i was hooked. I loved all the old ones and still pop them into my GBA every once and a while. But right now I'm TRYING to get all 386 of my pokemon to level 100 so I can transfer them over to pearl and diamond when it comes out.
They'll probably have some fail safe in there though, where you have to work your way up to being able to do that. Like with the time machine.