I like the ones you were listing, polomi. Half-Life 2 was a revolution, diverse and SO unique, Natural Selection 2 is the definite version of this unique type of asymmetric shooter / strategy mix & Serious Sam is just a parody of all the shooters that take themselves too seriously and therefore trashy in the best way. I'd name Bioshock Infinite as well, since it has some awesome storytelling, visuals and atmosphere.
If Playtonic decide to make a shooter, it's got to be a very unique one. I didn't play Perfect Dark or GoldenEye 007, but from the look of it, I'm not so certain whether these games would stand out nowadays. But maybe someone can explain to me what made these games so great in their times (except of being the first great shooters on a home console).
Anyways, it's possible to turn & twist the shooter genre nowadays - just look at Splatoon.