Irridium said:
Halo's mind-boggling success probably had something to do with it.
Then Call Of Duty 4 doubled that.
Roots go back a lot further. The FPS has been one of the most popular genres in PC gaming since 1993's Doom. For console players, it was the most popular game genre they barely played, so when Halo successfully translated the modern FPS to the consoles (Goldeneye never got the whole aiming on the z-axis down), it wasn't the case of a new emerging genre filled with unexplored potential taking root; it was the invasion of a well-oiled war machine already mired in the cliches that PC gamers were all too willing to blame on Halo.
The space marine as the default protagonist: 1993's Doom.
The first AAA brown shooter: 1996's Quake.
Extremely linear game levels: 1998's Half-Life wasn't the first.
Basic weapon set of melee weapon, pistol, shotgun, assault rifle, rocket launcher, grenades, sniper rifle (or sci-fi equivalents)... default by 1999's Quake 3.
In any case, consoles witness something fairly unique in gaming. A completely developed game genre that they were largely ignorant of hit them with the double-barrels of novelty and finely honed & crafted game-play. These days the novelty value has long ago but there's not exactly a whole lot of newer genres to pick up the baton.
That and the Unreal Engine makes them really easy to develop. Again, thank PC gaming for that one, since engine licensing has been big business since the Quake days.