1. No. However, I am running 64-bit Linux! I also have 64-bit Windows on another partition, but I haven't launched it for three months now. There is not much Windows can do that Linux cannot.
2. Yes. Most through Wine, however. That's why I'd be very interested in native Linux games.
3. Definitely. And it doesn't matter if it brings more optimisations or not. What people fail to understand is that Windows will outright drop 32-bit support in the future. Already 32-bit apps are emulated, and in the future, they will only be played through a virtual machine or an emulator, like DOS games are nowadays. Besides, compiling a game for 64-bit targets is not difficult. At least with GCC, although Linux had complete 64-bit support for years now (there is not a single 32-bit app being run on my computer right now). I hear the 64-bit compiler support on Windows is quite a bit worse, however.