[SUGGESTION] Change x86 march flag to "pentium3"

No, it's still not. Goto ubuntu.com → download → desktop → see the dropdown list with selected line '32bit (recommended)'. So they still fail ;-)

There has been some movement but as you have pointed out, it isn't far enough:

Unless you have specific reasons to choose 32-bit, we recommend 64-bit to utilise the full capacity of your hardware.

https://help.ubuntu.com/community/32bit_and_64bit

An exception I would consider making is the first 64-bit Pentium 4 processors. They tend to be slower in 64-bit than 32-bit and were not around for long before being replaced with the first Core processor.

and it takes more then slapping a compiler flag on it to put the full benefit of sse2

Now you may be talking about writing code specific for instruction sets. This would be possible and there is already some SSE specific code paths in place but all of this requires engine changes with multiple code paths being written in. This will happen more and more in time but obviously coders have other, higher return things to be doing.

even on lowest settings @ 1024x768 xonotic requires at least a 2.8Gz P4 and a 6600GT AGP

I beg to differ. I've tried Xonotic on an Athlon XP 2400+ with a 6600GT and it is VERY playable. 80fps on low settings at 1024x768, 50fps on normal even at 1600x1200, no crazy tweaks, no overclocking, just the default settings on The Big Benchmark. If you have benchmark results to the contrary I'd be happy to show you how to set your computer up properly ;-) .

if someone is running something that old then to hell with them sorry but it is what it is you can't please everyone and I see no sense in putting forth more then marginal effort so dog slow machines can run at 30fps vrs 25Fps not in a twitch based game like xonotic

I'm seeing a whole load of attitude here and no substance to back it up. You also outright, rudely decline the polite request of a moderator that you punctuate your posts. Searching through your past posts shows the same issues throughout. Please bear in mind this kind of attitude is not welcome.