I've never played into Sapphire, I've only used it for the Shiny Hunting. I originally played, rocked, and deeply loved Ruby. I never played Emerald until recently when I reordered it offline and my, I have no regrets. The graphics for it are so much better, they introduced pokemon from the previous regions sooner and early (which they repeated in for games like Platinum and B/W2). I've never played Diamond or Pearl, but I need to buy one of them so I can get a Spiritomb for my Platinum. I need at least two of the 4th Gen main games. I also buy and collect random books, so I've gotten my hands on a Platinum official Guide, a special edition official guide for Black/White, and the first of two volumes for the official guide for HG/SS (it only covers the Johto region and first 8 badges). I usually help my friends out by looking things up for that. xD
Oh geez! You don't even know, man. It's nuts. Every time I got into a different section, I lose my mind reading stuff. In fact, last night I was sucked into the roleplaying section. I have a roleplayer for seven or eight years, so that appealed greatly to be. If I can find the time away from other things, that is definitely something I want to dip into. I've only been here for one day, and I'm trying to tell my other friends all about it. If not only for the fun people, huge community, and good read, but for the wide options of things and interactions that can occur.
I only played Pokemon games from 3rd Generation onward as well like you did, so we do have something in common already! I specifically played Ruby/Sapphire/Emerald as well as all the 4th and 5th Generation main games. The only ones of those generations I never played was FireRed & LeafGreen but at least I managed to experience most of the good ones.