Half-Life 4 will come out on as it seems Valve can count to 3 when it comes to release dates, just not game titles. But if you only want to play a FPS with fast action and good story than play half life 2. If you really want to immerse yourself in the lore of Half-life universe than yes, you should play half life 1, half life blue shift and half life opposing force before playing half life 2. Half Life: Decay (skippable – PS2 only).The recommended playing order is pretty much the release order: What is the order of the Half Life games?