half-life was a really interesting game, and half-life 2 was even better. I think it played a huge role in ramping valve up to where they are today with steam. I know everyone wants half-life 3 but I think it's ok they have worked on other things because another FPS doesn't have nearly as much impact as what else they decided to do, but these games will always have a place in gaming history, their legacy is quite great :)