I have been contemplating starting over on Black since I stalled there and X has motivated me to go back and so I could get you copies of pokemon from Black and HeartGold. My sister has White and SoulSilver so I could get those for you through her. Give me a list and I'll see what she has.
Heart gold gets me alot of legendary Pokemon. Let's see,
Raikou and Entei can be found wandering around Johto, I'd say use a dugtrio or something to trap them(they both know roar, I just checked, so it would be a bit of a waste to spend a turn using mean look when you could be throwing more balls.)
Suicune has its own little side thing going for it.
Ho-oh and Lugia are fairly easy to get as well.
Groudon and Kyogre can be found in some tower using the red orb and blue orb (groudon's only in SS, Kyogre is in HG.)
If you have both of them in your party you can talk to someone and he'll give you the jade orb so you can get Rayquaza.
Latios and latias both roam around in kanto based on which version you have.
I as mentioned above, haven't played B/W so
here