Yes, CS has changed A LOT since the 1.6 version. Since the original Counter Strike came out, it barely got any updates. After 3 games made by Valve and a game constantly getting updated (Global Offensive) obviously has change a lot. From just changing the game mechanics itself, adding new guns and making balances, the game is completely different from the original and is making changes for the community, now being more of a multiplayer and competitive game. So yes, though it may have some of the same features and characteristics, CS:GO is very different to the original Counter Strike (1.6)