I too liked both titles but enjoyed Doom 3 by a vast amount more than HL2. Doom 3 does everything it intended to do whereas HL2 tries and fails on too many occassions, the plot is loosely told and has no resolution whatsoever, instead provides a cop-out sequel ending. Personally if I'm being told I'm fighting for some sort of purpose for 10 hours I want to see the result of that fight.
It's AI too was disappointing, I'd go so far to say it was on the same level as Doom 3's zombie AI only it's that Doom 3 has an excuse, it's
zombie AI.
Also, graphically HL2 may look a bit better than Doom 3 due to it's outdoor settings but in technical sense that is farther away from the truth than possible. Take a look at this for example:
http://www.doom3world.org/phpbb2/vie...t=7510&start=0 It's HL2 on the Doom 3 engine, it looks so much better on id new engine.
There was a quote I heard not too long ago "Doom 3 is the first in next generation gaming engines where Half-Life 2 is the last in the current generation". I couldn't agree more.
But more to the point, the game itself felt cold and stolid and almost as if the game was designed to show off the engine as opposed to the engine designed to show off the game. At the end of the day I doubt I'll be bothered to play HL2 again in a hurry.
EDIT: One last thing, the darkness in HL2 was obtrusive and your flashlight was useless unless you were facing a wall. In Doom 3 though it was a little annoying have to switch back and forth using the flashlight it served a much greater and effective purpose. In HL2 I just turned the Gamma settings up because it annoyed me so much, in Doom 3 I was content with the even darkness because it was a part of the gameplay mechanic.