How the hell did you get the '3' like that?
Hold down the Alt key, dial in 0179 on the numpad, and then release Alt. Though you might have to do it in Notepad and copy-paste, since typing that sequence of numbers can make some net browsers do funny things.
As for me, I didn't hate DOOM³, but I was certainly underwhelmed. As was mentioned before, it's far too linear, lacking the awesome secrets and hidden levels of its predecessors, not really adding anything new in higher skill settings, and basically forcing you down one path all the way through. Listening to audio recordings to get locker combos in replays is also extremely tedious.
I applaud it for trying to go for a darker, scarier tone, since I honestly thought the original DOOM was terrifying when I first played it, and hoped DOOM³ would recapture some of that. However, it's not nearly as disturbing as I'd hoped, with stuff like the "They took my baby" segment being totally wasted and pointless. However, it's honestly pretty solid at creating tension, and I'm basically always on-edge while I'm playing the game, so it gets points for managing that.
Technically, the art design is brilliant and extremely detailed, with the level designers obviously spending untold hours stringing up power cords, placing support beams, installing computer displays and much more. Stylistically, though, it's insanely gray and dull, much more boring to look at than the surprisingly-vibrant, old DOOM games. I was also hoping for area designs that were a bit more surreal and fantastical, like Episode 2 of the original DOOM, but it was basically just endless techbase maps that all kind of blended together. Having so few outdoor excursions (and making them annoying by basically giving you a time limit) didn't help, either.
While the weapons aren't as fun to use as in the old DOOM games, it's honestly a better balance. You can no longer just shotgun your way to victory in all situations, and most choose between the extremely powerful but pitifully-short-ranged shotgun, or the much-more-accurate but weaker machinegun. I like how it made the weapons more specialized like that, even if they weren't as satisfying. And the grenades were kind of pointless.
The almost complete lack of music was a real downer. I missed the soundtracks of the old DOOM games so much. If they weren't appropriate, they could've at least used something like the ambient music in DOOM 64, but instead, it's just annoying emptiness. On the plus side, the ambient sounds themselves were well-done, and I'd like if more classic DOOM mods used similar ambient sound design.
The action was obviously toned down quite a bit, which didn't bother me too much, since I don't view DOOM as Serious Sam's predecessor. However, the Resurrection of Evil expansion pack did beef up the enemy count and had some notably larger firefights in a few spots, and I won't pretend it wasn't a little appreciated.
Overall, I think that for everything the game got right, it ended up getting something else wrong, which left it as a bit of a middling experience. I've still beaten it several times, which is much more than I can say for many games I've played, but it just doesn't command my devotion as the original DOOM games did.