I have to admit to not being a gamer (unless you count almost not graduating HS and college due to various versions of Civilization)...so I cannot help much there...but I think you may run into issues with a 64bit version of linux and WINE or Cedega...but not sure.

Personally, I'm really on a Ubuntu kick. I have admitted before that I hated it for the longest time, but the more I use it, the more I love it. If you are a power user you might enjoy Kubuntu better simply b/c the KDE desktop is more confgurable than Gnome.

What I like about Ubuntu:
Package management - I've grown to love Apt-get and Synaptic... there are a few packages that dont work as well as compiling or getting the offical (Azureus is one) but for the most part it just works... you search synaptic for something like "gimp", it finds it, all of its dependancies and installs them...boom its in your Graphics Applications menu (btw gimp sucks).

Speed - I have two boxes that are EXACTLY the same, one running Suse 10.2 the other running Ubuntu, the Ubuntu box smokes the Suse box...its not even close

UI - I like their baby-sh_t theme...it grew on me...very clean

Ethos - I like what they are trying to do... free, open source software for everyone. Its an idea that really appeals to me for some reason.

Thats my recommendation - Ubuntu!