Yes, Half Life 2 is a perfect game for VR, and HLVR is the perfect composition !
And of course HLVR is a lot more cool and incredible game than original HL2...
But about others:
- Left4Dead, looks like it is possible to make similar mod, but developers assist required, because there is no SDK for it as far as I know...
- Bioshock series = all of them based on Unreal engine, and there is two options - ask developer assist to get required files... or disassemble controls input files and make a mod with separate head and gun tracking. There is a lot of open projects based on UDK, so it is possible...
- Crysis1 = Nathan Andrews proved that it is possible, he already did separate head and gun tracking in his demo, without 1:1 gun track however, but it looks very epic too !!! I'd wish they make a CryVR mod for Crysis1 (Crysis 2 and 3 not so interesting)
- Fallout 3 = it is really possible to make similar VR mod. Existing SDK and other tools is enough for it. There was a man who changed models animation to new smooth and real movement in the game... (ReAnimation mod). And there was a lot of modified gun models and item models... So no doubt - it is possible.
The only thing is - this kind of stuff required a team, who will make all this. But, even if someday someone will make VR mods for those games, I will definitely buy it !!! 50$ 100$ whatever ! TriDef and VorpX costs from 25 to 50 $ but only gives headtracking in games without freeaim and other VR features...