A generic FPS is one that does exactly (or really close) what every FPS before it has done.
Halo 3 - It was Halo 2 with a new coat of paint which was Halo 1 with a new coat of paint. The gameplay in Halo can be found in any number of FPs games and that makes it pretty generic. I suppose it did at least have 45 player co-op which helped.
Gears 2 - Looks to be like Gears 1 with some new gameplay mechanics and color but still Gears. Gears 2 gameplay has been copied and done several times, but Gears pacing and gameplay still feels different enough.
Killzone 2 - Nothing about that games seems new.
Portal - Brought a fresh new gun to the mix
Half-Life 2 - Was heavily physics based FPS in a world where there were not a lot of physics based FPS's. They also introduced us to the gravity gun.
Bioshock - Plasmids brought a semi-new twist to console players and the atmosphere was amazing.
