iainmet: I honestly dont think that will be a Steam issue in all fairness. Trouble is there is so much going on when that game starts up could be anything causing the issue.
spinefarm: It's kinda Steam issue cause they sell games that don't work :) They should test the games before selling them like GOG do
You do get occasional issues with GOG releases also, look in the support sections for the games here, you will see endless help requests due to bugs and errors, its one of those things with PC gaming.
Valve will test the games before it is put out on their platform just like GOG test them. Thing is though, there are so many PC configurations out there it is impossible to rest it on every last thing that the game could be running on. The issues you are having with Bioshock 2 would most likely be a minority. I should imagine that the users that have no issues whatsoever would far outweigh the ones with problems.
Valve also just put the stuff up on their store, the code for the exe file literally just gets modified slightly so the platform mentions you are in said game you are launching and also forces Steam client to open if you hit the exe in the install directory.
Most cases when there is an issue it is down to the devs not doing enough testing on different configurations before putting the game out. You even get weird issues with console games at times, look at the engine problem Skyrim was having on the PS3 until recently they finally managed to fix the performance drop out nicknamed Rimlag. Is that Sonys fault with the way they created the PS3 architecture, no it was Bethesda not doing enough testing.
I have way over 100 games in my Steam library and only 2 cause me issues. Ghost Master doesnt like to start occasionally, so will purchase it for a third time on GOG at somepoint, other game is Vampire : Bloodlines, I did get this working with the community patch but Steam removed the fixes and borked it again! That was an annoying one.
This is one of those things with PC gaming, it either works like a dream or everything can go wrong in a chain of events. Saying that it is Steams fault a game wont start doesnt really sit right. You have to look at all factors when the game is launching, it could even be down to something on your PC stopping it from running, it could be something to do with GFWL. It has been known that certain AV programs can stop things from running, putting the exe into a quarantine because it doesnt know what it is! Getting a fixed exe file covers a multitude of sins, in a lot of those files if you read the info that comes with them, they actually have to fix hooks in the programming that the developers have actually missed which causes issues for some users.