3 titles on your list don't belong there. Ep2, Portal and TF2 are not available and Valve offering up a release date doesn't mean a hell of a lot.
CSS came with HL2 as the multiplayer. DooM3 came with multiplayer, too and that's something nobody will be bragging about anytime soon, to be fair. Still. Lost Coast, which I loved, was just one level which the voiceovers in Lost Coast spend a lot of time telling you they'd already made and cut from HL2. HL2DM was a map or 3 when released. DoDs was a Valve release, sure. But I'm not certain that wasn't already in development and Valve acquired them at the last minute before making HL2 available for pre-orders.
Epic have done UT2004. At least one and I'm pretty sure it's two large download packs for it. Haven't had UT2K4 loaded for ages, but there were a couple of big bonus packs for it. Neither of which cost anything. Gears of War, which I also mentioned. And Gears of War is a SP and MP and Co-Op game. I can understand you don't play consoles, but you have a look at Gears of War and it's worth more than everything on your Valve list combined, except for HL2 itself. And UT2K7 or is it 8 these days, won't be far behind, possibly before(?) Ep2, TF2 and Portal, which Valves also didn't make from the start.
You could argue this one all day long. Valve are like Microsoft and the famous three E's. Embrace it, Extend it to work with Windows (in this case, extend it to fit the HL2 universe) and exterminate any memory of who originally did it.
As for id. They've not done a lot, but they have less than a third the staff, have told me no lies, didn't lose all their source code and have to send everyone on an extended training camp to join the FBI to learn about tracking criminal hackers, to only then go back to making a game. Also Carmack doesn't spend a lot of times shouting from the rooftops about how big his dick is, unlike Valve or Epic.
So, I'd still not be shouting about volumes of work. And unless Carmack is a liar and, quite frankly, I doubt it. HL2 still has Quake code in it, so I suppose we may as well give id credit for everything Valve's done and immediately they start to look like a darn industrious bunch down there in Dallas;P