Registeel, Kyogre, Rayquaza, Deoxis,
Phione, Victini, Tornadus, Thundurus, Landorus, Zekrom,
Kyurem, Meloetta e Genesect.
These are all the legendaries I never caught in a Generation 4 game and beyond. I have Kyogre and Rayquaza, but only in Sapphire. I must've had Registeel at some point, because I do have Regigigas, but if that's the case, then I no longer. The only reason I don't have Phione it's because of lazyness, so it doesn't count. I don't have all of those Generation 5 legendaries because I barely played the games after I finished them, and I was out of the Pokemon scene for most of Gen 5.
After I get all of these and transfer them to Gen 6 when Poke Transfer comes out, all I will need is a Mudkip (because I chose Treecko in Soul Silver and Torchic was free in X and Y) and I'll be GOLDEN, the rest of the Pokemon I still haven't registered will be a piece of cake to get.
I just feel I NEED to post this:

Remember back then when Game Freak actually balanced the games? Yeah, me neither.