Go eat a kikkeli, Lare.
I too think that it was not because of HL 2 that physics became so popular. Other fps', namely FarCry had them before and for example Max Payne 2 really showed off, not only with graphics but the various after effects to enviroment after battles. Stuff explodes, people topple shelves when they die and stuff rolls around the floor and behind the corner. All that jazz. Physics were already becoming a standard. Part of that is thanks to the amazing E3 videos of Traptown and whatnot though. HL 2 just came and showed that, "dude, you can do all this **** with Havok" and gradually Havok physics became a standard.
As for who was the first? I think it might have been one of the Fifa games. Or Thief: The Dark Project.