I saw this amazing video containing all Japanese Nissan Skyline commercials being announced a few weeks back on a Minkara blog:
Nissan Skyline Japanese commercials collection
Nissan Skyline Japanese commercials collection
This DVD covers almost all models: from the second generation (S50), third generation (C10 aka hakosuka), fourth (C110 aka Kenmeri) and up to the tenth generation (R34)!

I was able to find the DVD on Amazon Japan (?????? CM?????? [DVD]), but I haven’t seen it for sale elsewhere… Now if only the shipping costs from Japan weren’t that steep… :(