This is just a random post off IMDb, but he sums up HL2 so precisely:
If you think this game is groundbreaking then you're either a moron or you haven't been playing PC games for very long.
There is absolutely nothing in this game that hasn't been done before.
Physics and ragdolls? We've seen them in Max Payne 2, Raven Shield, and countless others. They've been around for years.
Mankind threatened by aliens and its up to you, a one-man army to stop them - Oh yeah, real original plot right there. Duke Nukem 3D did this sort of thing better, and with more style and humor.
Can you interact with any of the NPCs? Nope. Can you ever deviate from the linear course of the game? Nope. Sure you're given vehicles but you can't explore the environment because it doesn't allow for any exploration.
Then there's the incoherent plot, cliched and horribly inane dialogue, and a complete lack of interesting enemies that made the first Half Life so memorable. Story? What story? Character development? A generic NPC named Alex that falls in love with a character who never speaks? Give me a break. Don't even get me started on that awful anticlimactic ending.
Multiplayer, what a joke. Valve couldn't even ship the game with deathmatch, and when they did release it, it was only two damn levels.
Ah, Steam, what a complete load of sh*t. Takes a *beep* hour to install, and then chews up memory and hinders the game's performance. Nice going Valve, what a way to sh*t on the consumers just because you want to protect your profits. Instead of trying to stop pirates, who will never be stopped, do something about the cheating in multiplayer.
Graphics are okay, and the sound is pretty good, but again, I've seen better.
Coming from someone who has been playing FPSs for over a decade, I can say that Half Life 2 wins the Most Overrated Game Ever award. And now I can already tell that all the Half Life fanboys are going to start crying here. So flame away.