I played them all and my favorite was the Gold edition. It was magical. The whole game just felt perfect and it was the first and only Pokemon game, in which I`ve collected all Pokemons (Yeah, we even used that cable to transfer the Pokemon and all these things).
So my vote goes for Gold, just because I like Ho-Oh. But personally I think there is not much of a difference between the different versions of the respective generation of Pokemon-games and that`s why I would summarize Gold/Silver, Blue/Red and the others into one respective category...
I played Red, then Yellow, then Crystal, then Sliver and Gold, and then Blue (dunno why I played that last), then Emerald, then Ruby (only lasted half-way), Sapphire (1/2 too, cause I already played Emerald), then Pearl, and then Diamond, Out of all, I loved Crystal the most, but since it's not there I vote for Silver.
I never knew there was a Pokemon OHSNAP! Version...lolhotlinking Never mind, the images don't even work normally.
Back on topic...My favorite version is Blue. It was the first one I played, and it has my favorite region...I know G/S/C have Kanto, but it just doesn't have the same feel, since a few things are different (Like Cinnabar Island being destroyed). I can't wait to see Kanto in SoulSilver when I get it (Hopefully today after school).
Blue was the first Pokemon game I played but it has to be Silver. I loved that game from the moment I got it right up till that fateful Christmas Day in 2004 when I left it in my GB Player on the Gamecube and my brothers mate yanked the controller down thus snapping the cartridge in two (he did a similar thing to my Wii and snapped the top plate for GC controllers off). It had my first ever level 100 on it as well which was Vaporeon.