Descent and Quake were both 3D shooters and DOS games, and Halo came out a year earlier with "better graphics"; CS was neither the first 3D shooter nor the first Windows game in its genre. Also, the first Counter-Strike was not a completely new game -- it used a modified Half-Life engine (which itself was built on the Quake engine).

Sure, CS was arguably the most popular and long-lasting of the FPS of that era -- but let's not pretend that that was because of technical superiority, it won out because of gameplay.