Actually, quiet a number of people would disagree with that comment... HL2 is absolutely mind blowing in atmosphere, physics, textures, lighting and everything technical. I myself have not actually sat down and play the game through, so I can't really comment on the storyline, but I can't wait for some money to flow in so I can buy it.
The HL2 story line isn't the greatest, but I keep playing on and on. It doesn't get old like Doom 3 does; I think I'll actually finish this one. The atmosphere is amazing, though. It's so immersive and everything is self-consistant. The only thing that messes up the immersion is the lack of control over objects held; there should be a way to rotate objects while you're holding them.
I agree the environments are nice though. But I couldn't help telling myself like "Well.. this is going to happen next, so watch out for..." and it happened