Topic: Which Pokemon title should I buy?

I've only played Pokemon TCG on Gameboy Color, and one of the Pokemon games that were published for the very same console. I skipped all GBA titles, but now I'm planing on buying one for the DS, as I found them for a very low price at around 5-10 dollars. So, my obvious question would be: Which one should I buy? I'd like to hear your experiences with Pokemon DS games, and if you're so kind as to explain to me the differences among the titles, I would be ever so grateful .

Please use the DS recommendations thread to ask for opinions regarding which DS game to purchase. Thank you :3