THEY ARE THE BEST GAMES EVER! Especially XD, as it is just more advanced and better! (ok not totally, but overall unless you prefer the story or pokemon availability of Colosseum better, XD is the one to get for sure). Of course, these games were especially awesome back before heartgold and soulsilver came out because then it was the only way to legitimately get a lot of johto pokemon, including the starters and lugia and ho-oh, into your games (well you could get the starters in emerald but it is a little hard and annoying to catch 200 pokemon and all. Really, when you think back on it, until HG/SS, lugia and ho-oh were almost as rare and valuable and sought after as like mew and deoxys....but anyway that's besides the point. The games both have such fun stories and awesome battle visuals/graphics that only black/white have come close too. Now, once X and Y come out we might be seeing some fondly similar styles of battling to colosseum and XD...but until then the battles of XD and colosseum are still one of a kind (or should I say two of a kind lol :P).
I'm sorta back
While I'd always love to talk about anything pokemon, I will only be using the 6th gen Wifi section for a while out of efficiency in my life, unfortunately
My 3DS friend code is 0576 3520 6954