I never could take Counter-Strike (or the source engine) seriously because of the general lack of iron sights.
I seem to remember iron sights on Counterstrike. Of course, I am talking about the original, since I don't think I have played Counterstrike Source. I am nearly positive there were iron sites, I remember seeing them on the Desert Eagle, and seem to remember them on the M4.
That tells you the last time I really played MP FPS, since I haven't really played FPSes in MP since the original Counterstrike. It was the immaturity of the players in that game that really made the genre not worth it to me.