Again, as the other guys have said, most distro's will run the games if you install the emulator. And some vendors have even ported their stuff to linux.
Doom3, Unreal Tournament, Quake all have linux ports, hence running "natively". ID basically are aimign to release all their games cross platform. Some great little games are born out of the Linux environment as well. For a great time killer at work, try Foobillard. It's pretty sweet, and has a Windows port as well.
With regards to OpenOffice, it will most definitely run on linux, as that is it's primary development platform. It was originally StarOffice from Sun, and they then released an open source version for public working. It was released in order for them to see what user demand required in an office suite. They would then take the popular ideas and add it to their commercial Star Office suite. However the rate at which it expanded in the open source world was too rapid for Sun to try and keep up with it, so they released it and it has taken off. They keep patent on certain bits of code, and have a division which actively maintains the code. The beauty of OpenOffice as an office suite is that it will run on almost any platform you would want an office suite to run on.
Drivers in linux have always been a contentious issue. If you stick to buying mainstream hardware you'll be fine. Start buying obscure components and you may have a problem. Just a warning, wireless drivers can be rough. And try stick to nVidia cards for linux. Soft modems can be tough as well.