You have? and more importantly where?
Here is something I am working at the moment and you can clearly see how powerfull the doom³-engine can be even at huge outdoor-scenes.....
The Doom 3 engine is WAY the fuck more powerful than Half Life 2. It'll be a couple years before we see great stuff made with it, though. Here's hoping Raven pulls it off with Quake 4.
HL2 was outdated long before release. It'll be the cheap engine to get for new developers. A year from now it will look ancient. Without the excellent use of physics we'd be nitpicking the awful textures.
The most impressive engine by far is Far Cry. There's no argument. With everything maxed it looks and runs great. Doom 3 looks great maxed out but hardly runs. And HL2 looks ok and runs amazing. Far Cry is the only one to combine everything and make it work. Too bad each patch finds a new way to break it. And with a dead community you have a real sad situation.
As far as gameplay is concerned it's a toss-up between Far Cry's originality and HL2's successful refinement of what's already been done. Doom 3 didn't improve anything