@srgt.scales: Thanks but what about the recording software, video encoder and settings? And what's also interesting me is how many MB per minute do your videos have in average? Mine are about 75.6MB/minute which is pretty much already, considering my internet provider contract allows for just 7.5MB/minute (1024kbit/s) upload speed.
EDIT: I have done some tests and here are the results (always 1080HD):
10.000kb/s, MPEG-1 -> MPEG-1 creates sharper videos than the Xvid codec but more artifacts. The size is at 72MB/m.
10.000kb/s, Xvid (my default setting) -> Artifacts and blurs on moving surfaces, 70,45MB/m.
15.000kb/s, Xvid -> Hardly visible artifacts but as blurry as 10.000kb/s
20.000kb/s, Xvid -> No visible artifacts but still not as sharp as the graphics in game, 133,68MB/m.
20.000kb/s, MPEG-1 -> No visible artifacts and the sharpest result of all, 138,8MB/m
30.000kbs, Xvid -> I had to watch the video several times and also do several cross comparisons with the 20000kb/s Xvid version and I seem to see a slight increase in sharpness but that's probably subjective, 203,79MB/m.
Finally I put it to the extreme with
100.000kbs, Xvid -> no visible difference to 30000kb/s but 608MB/m! Also the data transfer rate is so high that the game got frozen for a split second somehere in the middle of the test!
So my conclusion is that MPEG-1 with 20.000kb/s is the best choice.