I am gonna be one of thos smug gits who steps in and says
MTW2, are you kidding my copy plus expansion pack works perfectly. Mind you you do know that it's 'buggyness' as you describe it is more than likely down to the Securom anti piracy software it installs. Remember reading a bout people who had installed other Securom protected games; Bioshock, STALKER, Spore etc having problems getting other Securom games to install, patch update and run in general.
I also notice a lot of folk saying Oblivion, lol that's another game I never had any problems with.
Stalker on the other hand, BSOD every time you moved between areas, turned out to be a conflict with Nvida's new memory leak fixed drivers for the 8series GPUs. I have to run year old drivers to get the game to work. I also read about Clear Sky and it's serious bug issues so I am still thinking about weather to purchase that game or not.
Gmod can be twitchy as well, especially since it allows any old crap created by any triple thumbed goon to run on it, right up until it locks up and goes off for a coffee and fag break.