What you need to do is to somehow analyze the upload and have 3
different display modes; 4:3, 16:10 and 16:9

And have the youtube page(s) display the video size depending on the
aspect ratio.

It's easy to do and it will make it not look ugly in 90% of all
videos :P

While we're on the subject, I really really do hope you guys keep high
def. streaming support for all apsect ratios and allow embedding, if
you do this- us gamers will have our new home here on youtube.

We have been looking for a new home ever since stage6 shut down, most
other video stream websites reject us (vimeo, exposureroom, et.c.) and
bans video game videos...

If you guys keep high def streaming/embedding and allow video games
you will make the entire video game community such a huge favor that
it's hard to say in words.

Please do everything you can to keep this a reality (maybe add short
5sec advertisements (that explains "video will begin in Xseconds"
clearly) at the start of the video if you're embedding high def. video
to make up some of the bandwidth money)