Topic moved. The WiFi Pokemon board isn't for trading, it's for the online-based aspects of Pokemon games only. Anything else goes on this forum. You're not the first, and definitely won't be the last, but please take note of forum descriptions when making a new thread.
Anyways, SteelixFan answered your question. If you want those rare one-shots like the starters or the non-Sinnoh legendaries, you'll need to trade with someone else for them or migrate them over from the Advance gen games. It makes perfect sense, mind. You couldn't trade R/S/E/FR/LG with G/S/C/R/B/Y for coding reasons, and seeing that D/P is built off of them it's no different.