I suppose you haven't played Pokemon before the 4th gen?
Its the same with the normal ones
Red / Blue / Green (Jap only) - Yellow
Gold / Silver - Crystal
Ruby / Sapphire - Emerald
Diamond / Pearl - Platinum
I have to say the Emerald is probably the best of the remakes of the main series.
So, you've probably got it by now. I didn't play T/D neither D/P (well, Diamond a little on PC emulator, but I didn't like it at the start.. Now, on my DS I have Platinum and it feels way better), I directly took Platinum and EoTS right away. Quite happy with them too.
About the starter - I got Pikachu AGAIN in EoTS, so I sticked to him and to the nickname Pika, same as in Red Rescue Team.
The only thing that was bad is.. That you share the money, AND, you don't have an awesome base like in the original ones. (After CERTAIN storyline points, that I won't explain as it's a spoiler)