Problem with youtube!! Help please!

Hi, i'm from Italy (sorry for my bad english), and i have a problem with my video and youtube. I buyed a Lumix Gh3 for shooting videoclips. I take some footage in .mov 25 fps, and i created a premiere cs6 project with the same quality (1920x1080 25fps) and then, i exported all in h.264 25fps and high bitrate for better quality. After this my video looks great and then i uploaded it on youtube; the problem is that youtube "kills" my quality too much! There are so many user that have my same camera and their shoots are very pretty and impressive, then mine is very very pixelated... in 480p is bad, and in 1080 is acceptable. I don't know how to fix this, is like 5 days i spent to fix this but all is awful. Please if someone can help me i will be very grateful, because i need to fix this for work! thanks for the attention and i hope to fix that :)
a sample of my videos
http://www.youtube.com/watch?v=VALBtTkcqQ8
http://www.youtube.com/watch?v=DQjtKSdK-QM

and then a comparison with another video of my camera founded on youtube
http://www.youtube.com/watch?v=AYNsDiMe_74

Thanks
Alex