So in your opinion what is the single biggest innovation to console gaming this generation?

• Online Multiplayer - With Xbox Live came a brilliant ableit juvenile community.  Every game was instantly connected to thousands of people and competitive multiplayer and co-op experiences became the norm making gaming a social experience.
• Motion Controls - The Wii isn't a graphical powerhouse but it did bring something that opened the doors for 10's of millions new gamers -- motion controls.  Everyone from my six year old nephew to my 80 year old nana bought a Wii because of the new control optioned that immersed them even further into the games.
• Achievements - With Xbox Live came multiplayer and achievements.  Multiplayer let you play with friends from your couch and achievements gave you a reason to play and keep playing.  By dangling a prize in front of the player with a description that's even short for twitter, gamers did things they normal wouldn't do and played more than they normally would have played.
• Technological Leap - It's no secret that the Xbox was a giant in the looks department.  Look at a Gamecube, PS2, or Xbox game and compare it to a launch Xbox 360 game and the difference is insane.  Now, with the PS3 out and several years into both consoles, looking at a recent PS3 or Xbox 360 and comparing that to a launch Xbox 360 game and the difference is night and day.  Games have made a huge leaps and bounds in the overall size and look in three short years that is just incredible impressive.
• Downloadable Content - Ah, horse armor, so expensive and so worthless.  Sure, we laugh but no with DLC we can expand our games by having regular content delivered to us for a price.  Sometimes, like in the case of horse armor, it's a joke, other times, like in the case of Borderlands, it's almost an entire new game!
• Other - Did I miss something?  Reply and let everyone knoe!

I think Heavy Rain is the biggest innovation, new style game-play and story based gaming/adventure gaming on a console platform is the best thing to come to consoles and I hope it grows.
Motion controls on the Wii are pretty kick-ass though.

I think DLC as an add-on to full price games is actually hindering this generation (This coming from a heavy PC gamer). I find it total BS to have to pay real money for an online map or a piece of clothing for a virtual character.

Online multi-player is nothing new to me (pc gamer side again)

Technological leap: It has made an impact mostly on graphics and the increase of space available has not been utilized to help improve game-play nearly as many games as it should.
Graphics improvements only go so far, game-play should be the what is aimed for more.

Achievements: I could care less about these. It can add replay value a little bit, but that is about it for me.

That sums it up.

I voted motion controls. They greatly change how we play games and adds a lot of gameplay options.

I cant say one is bigger than the other. 

All of them are huge and changed gaming as we know.

Motion controls. I hope more games use them sooner rather than later.

Other.

Gamer-centric game design. I hope more games will be more like that.

Motion controls. Never before have they been made a primary element of the game.

The Wii is evolutionary. The other innovations are also important but they are evolutionary.

DLC existed last generation -- it has just broadened in scope. Games have long had "achievements" -- they just went on-line. On-line multiplayer existed before -- it has just been enhanced. And each generation has made strides over the previous one in appearance.

Mike from Morgantown

Online for sure.

Motion controls are not quite there yet. It feels too awkward at the moment.

For me the biggest innovation is that the story telling medium has become more descriptive; this probably lends itself to the overall graphical power difference this generation of consoles has over the previous. I feel like I am looking at real people with real emotions, not to mention the great strides the industry has taken with full motion capture, audio effects, physics, and graphical techniques such as HDR, bloom, AA, and sophisticated shaders. I still feel that motion control has its place in gameplay and also its limits. Online as others have pointed out is nothing new to pc gamers so the infrastructure that is in place is different, but the over all content is nothing new (DLC, patches, etc).

Online

being a PS & nintendo gamer last gen I never played online games

for me it was online gaming.