Netrigan said:
It's kind of like saying all country music sounds alike or all heavy metal. It does... and it doesn't.
Take this link to TV Tropes.
http://tvtropes.org/pmwiki/pmwiki.php/Main/ASpaceMarineIsYou
A lot of the same basic tropes have been showing up in the same sci-fi military shooters since Doom, who stole most of them from ALIENS. And if you do happen to come up with something mildly new and your game is a big hit... said trope will likely show up in every subsequent game that comes out.
This is why lots of us PC old timers openly mock Halo fans who call the game innovative or original, because we see how 95% of the game is incredibly similar to what has come before. But a good game (and Halo is a good game, even if I don't like it) will have a certain something that separates it from the competition. It has a new game mechanic or it plays with the cliches in a slightly novel way. Something that fans of the genre can latch on to that makes it a unique playing experience... but something that non-fans will almost certainly miss, while catching the fact that you're yet another space marine battling yet another gang of alien bad guys who have yet again targeted Earth for destruction for yet again dubious reasons.
AHHHHHHHHHHHG.
why would you put up a link to tvtropes? now i'm doomed to wake up tomorrow with my face on my keyboard , with 42 unread tabs on my browser!
tvtropes slowly eating my life away aside, generic shooters were created when some developers were all like "oooooooo, look at call of duty and halo, and their enormous sales and popularity, we should get into that!"
or you'know something along those lines.
anyways now people now mostly hate on halo (probably doesn't help that microsoft is trying to milk the dead cow, even after bungie left), whilst CoD still lives but with not AS many people supporting it as before.