none of those games are ports, they were worked on by different teams cooperatively, thats how they were released at the same time on all platforms.
gears of war for example will be a port, since it wasnt orginally intended for the pc, and they have to manually take the code\models and make them compatible for the pc.
actually bioshock was ported from PC to 360
Originally Posted by http://arstechnica.com/journals/thumbs.ars/2007/08/13/hands-on-with-the-bioshock-demo-360
looks absolutely amazing on the 360, with a rock-solid framerate and control scheme. This is no second-class port, and I'm wavering in my conviction to buy the PC version.
there is only a 10FPS difference at 1024x768 but its weird because the ram isnt slowing it down though, because the 320mb OC gains 5FPS.
i didnt use these results since CoH wasnt released as a DX10 title and is completely un optimized for it.