Now that I'm nearing the end of SoulSilver story-line I've got to make a decision as to what game to go too next.  SoulSilver is the first one I've finished and now I want to go back and play and collect from the ones I'm missing. I own Pearl already and I've got a Darkrai and Deoxyes (sp) on the save file I was playing  but I'm wondering if I should buy Platinum instead. My question and the reason for this post:  Since I missed the original games should I play the remixed versions of games like Red/Blue (FireRed/LeafGreen) rather than hunt down the originals?  I still got my Gameboy Advance so I can still play the older Gameboy Color games but I'm worried that there may be differences between the original and remixed games that will cause me to feel like I'm missing out.   
 
Like, for example, you can only catch   Dialga, Palkia, and Giratina but you couldn't in the original Diamond/Pearl, right?  Things like this.

Don't play the originals. They feel totally archaic with slow movement and a clunky battle system. If you want, firered/leafgreen were both good versions of the originals. 
As for Platinum/Pearl/Diamond, if you already have one, there is no reason to get the slightly upgraded platinum version. It's just a waste of 30-40 bucks.

Red/Blue are also kind of imbalanced and buggy. Though, you may want to play it just to exploit those bugs.