No seriously, i don't know if it's a trend coming on in the fps history, but almost all endings in those games nowadays have a "fin en queue de poisson" as we say in french, maybe it's just to make a sequel for the game license or maybe it's a lack of imagination, i don't know.
HL2, Doom3, FEAR, Quake4, Painkiller, have crappy endings and it begins to be really annoying.