[Null]

Actually, HL2 is the first big step for FPS games in a long time. The gameplay is enhanced GREATLY by the phisics engine. And The phisics engine is going to shape FPS gaming for years to come.

This is the phisics engine that you mention enhances CS. the reason it doest do as much for CS right now as its doing for the game, is that most of CS Source is a port. when maps start coming out that really begin to use what that phisics engine is capable of, the gameplay will change tremendously. It'll cause players to use thier mind much more with the objects and stuff.

Then the possibilities become endless and people start using this to make new mods for the game.

From what it sounds like, HL2 has the first truly innovative gamplay in a FPS game MAYBE since HL1.