The layer responsible in Android is called PacketVideo - and it has limitations.
http://www.packetvideo.com/resources/OpenCORE_brochure.pdf
There's a competitor called CoreCodec that's been working at getting their stuff to play with Android since Apr 2009. According to one of their team, they expect the architectural changes for 2.2 will allow them to bind in their stuff in a way that they feel is appropriate.
That's doesn't mean a codec change on 2.2 from day one.
As for codecs making it out to computers - two things: 1) playback: you already have H.264 playback on an EVO for 720p at 24 fps - movie rates, pretty good for any phone, and 2) record: the best your computer has built in, if it has one at all, is probably the same as the phone's - H.263 for video conferencing.
The recording is truly crippled by the MPEG4 Part 2 codec, as opposed to MPEG4 Part 10 (H.264).
However - the EVO sensor and lens aren't particularly crappy - the main problem is the limited codec.
Competitors do have better sensors and lenses in some cases. A codec change won't fix that. For that, you just have to learn to live with disappointment.
Or to simply learn to work around it in your filming style.
