Why do you say that there isn't a default video player? My G2 plays back video I shoot with the camera.

If you're like me and have recently switched from Blackberry, you'll find that G2 uses different video formats than Blackberry. The AVIs that worked on Blackberry, for example, won't run on the G2. You'll have to convert them.

Here are the video formats supported by Android:

Android Supported Media Formats | Android Developers

I have used this online converter once to convert a video for the G2. I don't know if there are better converters...I used the first one I found:

http://video.online-convert.com/