As much as Epic basically has a said a big "Fuck You!" to us PC gamers, it's not their fault gaming is rather stagnant these days for certain genres, etc.
I'd say the real issues is that devs aren't looking to make the next great game.
They're looking to make the next big $$$-making hit, which is why the gaming world is starting to feel a lot like Hollywood to me, which is a horrible, horrible thing.
As for shooters than have "kept me going", i honestly had lost a lot of hope in my future in PC gaming after UT3 came out & disappointed me.
I still played it a lot initially, but it was not like 2k4, which was my favorite game of all time.
I never even had much interest in L4D initally, but it turned out i enjoyed it immensely.
L4D2 didn't have the same feel for me, so i've not played it much.
Borderlands was another one i never expected to to like so much, i mean shit, it's actually a port.
After de-consolizing the .ini files as much as i could, i quite like it, & got addicted to it, particularly the gun-collecting.
But i don't know what it'll be next, if there is anything...