HL2 is more than just the gravity gun. The art style, the open levels on the beaches, the facial animations, the improved storytelling from HL1, the antlion army, game was so much more than just an updated half life. Without HL2, portal wouldn't have any legs to stand on, valve took on narbacular drop, hired the team and put them to work on the source engine to make portal. Counter strike source was the defacto mp shooter for years if not decades, hell even the portal 2 goo came from half life 2 ep 3 just like they mention in the documentary. Saying they ignored all other aspects of the game for the gravity gun does half life 2 a disservice to what it accomplished.