Wii Sports and Call of Duty were easily the definitive games.

Games like Uncharted and Mario Galaxy were pretty minor blips in comparison.

Call of Duty
Halo 3
Gears of War/Uncharted
Elder Scrolls/Fallout

Come to mind on how I would describe last gen as a whole.

Wii:
Mario Galaxy 1 & 2 (showed how 3D plataforming can be awesome)
Xenoblade chronicles (Best RPG last gen)
Zelda: Skyward Sword (The only motion based game i enjoyed, shows it can be done)
Wii Sports (The broad appeal brought a lot of new people in to the gaming world)

PS3:
The Last of Us (Story telling, character development, cinematography with a good enough gameplay)
Heavy Rain (While the gameplay is not as solid as TLoU, it is almost even in everything else)
Ni No Kuni (An work of art, despite the battle system being a little lackluster gameplay wise)
Demon Souls/Dark Souls (Showing there is space for challenge)

PC:
TES:Skyrim (Showed open world wonders and how important it can be to allow gamers to create their content)
CoD 4:MW (started all this FPS fest, even if i don't enjoy it, it had impact)

My defining 7th gen experience was without a doubt Uncharted 2. I had never before nor since been so completely blown away by a game. I do believe UC3 was better, but it lacked that initial "Ho-ly shit" feeling that made UC2 stand out from everything else.

COD4
Fallout3
Skyrim
Mass Effect Trilogy
Bioshock Trilogy
Assassin's Creed
Portal / Portal 2
Minecraft
Wii Sports
Mario Galaxy
Uncharted
GTA5

I honestly can't believe people are listing "Infamous" lol anyways, mine are as follows:

Xbox 360:
Gears of War 1 and 3
Halo 3
Left 4 Dead
Alan Wake
Forza series
Fable
Dance Central

PS3:
Heavy Rain

Uncharted

Multiplatform:
Skyrim
Mass Effect
Bioshock

I think the games that defined last gen are the ones that had the most influence on devs and most gamers. Games that had aspects that gamers wanted most and that devs had to implement in their games to sell well.

Gears of War (may not be the first with cover mechanics but did it so well other games had to borrow it, also the way the camera shakes when you run... yep a lot of games borrowed that as well)

Uncharted (for it's cinematic approach and character development)

Mass Effect (all around rpg, cover system, deep story, real choices in dialogues, good/evil character devlopment)

Bioshock (incredible art style and ambiance can sell)

Call of Duty (So how many games are trying this formula?)

Elder Scrolls/Fallout (Bethesda knows open worlds and customization, so many rpgs tried to emulate these successful series)

Just Dance (like it or not musical games were a hit last gen, because of JD we got games like Dance Central, Zumba etc ... these games were very present last gen)

Halo (yep devs are still trying to make a Halo killer and still couldn't do it, last gen this franchise went as big as getting an anual release)

God of War (don't believe it when people tell you qte are bad, they like them in GOW. Also Even if only one decent GOW was released last gen, some games tried to replicate the formula, so it was very influential in it's genre)

Wiifit/Wiisports (ohh sure did, get off the couch and start training, yep those "games" were all over the place last gen, because of them both MS and Sony came up with their own versions)

Assassin's Creed (did you say platformer? what game does it better than AC... and those animations)

Final Fantasy 13 (only FF we got last gen... but they made what, 10 games out of it? geez)

Angry Birds (had to put it... really)

i will try to keep this at the msot essential titles that defined last generation

wii sports
bioshock
super mario galaxy
assasins creed
mass effect
wii play
mario kart wii
uncharted
guitar hero 3
rock band

and all the games that seem like they are referring to a franchise, they are not, they are referring to the first game that came out in the series. these are the games that paved the way for the way the generation went.

you have to do it by genre really
tps - uncharted 2
rpg - mass effect/skyrim
fps - COD
sports - fifa/madden
race- GT5
open world - assassins creed/ GTA 5

I think last gen for me. (at lest for most of the timeframe) was dominated by the Nintendo ds. I think it had the best line up of any console of all time and it was the first time a handheld became my primary gaming machine.