they are not saying that gears invented the coversystem they are saying that gears perfect the system and that other games try to copy it.

Mass Effect 3

This

The feeling if joy i had after finishing RDR, Mass Effect, Dead Space 1 and 2 was so good so i say one of them, although i am not sure RDR can be classified as a shooter. Assassinæs Creed is definitly not or that would be on my list too. Uncharted 1 and 2 was pretty unforgettable for me

I think I had unlimited amount of joy after finishing MGS4 and Grand Theft Auto 4 were truly unforgetable. But Uncharted 2 was just way too epic.

I'm gunna have to go with.......

If the beta is any indication, I can tell you that Gears of War 3 will be freaking EPIC. By far the best TPS franchise I have ever played.  

The original Gears for me, by a mile.  It set the standard in terms of what this generation of consoles was truly capable of, and the multiplayer kept me busy for well over a year.

My favorite TPS this generation, thus far, is Mass Effect 2. The game is a deep, engaging experience. My only concern with choosing it for this particular category is that I myself consider it more of an ARPG (action role-playing-game), but to each his or her own, I suppose.

A close second however, would be Dead Space 2. The gameplay is wonderful and I do not think such a thing can be denined or even ignored. The pacing, too, is excellent and of course, the horror is unforgettable.

Choose a game that came out in stores. No counting Beta's

In terms of a new IP, Assassins Creed was my favorite.  But the Batman: Arkham series might eclipse that once Arkham City comes out.  We'll just have to see.

I'm a sucker for free roaming/Metrovania type games.  And those two series hit the nail on the head.  I'd even venture to say they did 'Metroid' style progression and exploration better than Prime and Other M.