I'm pretty sure that after this next installment Mass Effect will end, so why people want it to end so badly now I don't know, besides, I like it. Also sports games with numbers at the end? If people like to play sports simulations then leave them to it, it's not like they try to win any awards that aren't categorised under "Sports", or that they are in any way harmful to the gaming community by existing is it?
Anyway, Halo should stop because it's fine where it is and it did it's job admirably during it's reign. Call Of Duty went from an improved Medal of Honour to it's own thing with Modern Warfare, that's respectable, but then it poked the gaming community with a stick saying "look, we're still not like Medal of Honour, it's modern! again!" It's tired, go to the far future or just do something else.
Finally, GTA. Don't get me wrong, I want another yet, the mix of GTA4 and San Andreas where fun and grit combine to become what GTA4 forgot to be is so promising. But theres only so many games where you can hide "Drive there, shoot them, take this, bring it back, I despite being a 35-60 adult will never offer to drive you anywhere" behind slightly altered stories and parody based humour. Rockstar have proven that they can innovate, Red Dead was a little flat mission wise but the story was more serious at times and the genre was cool. L.A Noire looks as if it may rock my world too. So basically, make new things Rockstar, keep innovating. And change your mission layouts to something other than violent games of tag and fetch.