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 have 2 Friend codes I use about equally. One is 4055-3723-1345 and the other is 0576 3520 6954. I'll try to mention which one to look for when needed, if I don't then ask.
I try to train pokemon with the best natures and IVs, but generally don't breed for IVs and occasionally use a pokemon that could have a better nature out of laziness (on the other hand I have reset or recaught the same species 20+ times to get the best nature and decent IVs sometimes). I somewhat do EV training, but don't calculate it out so it's perfect, just rely on the chart in the super training thing.