Last generation was largely defined by the rising popularity of motion control, the rise of western RPGs and action-adventure games, the official saturation of the "bro shooter" (although that started to some extent with Halo in the 6th gen), the resurgence of local co-op and platformers, the rise of mini-game compilations, and towards the end of last gen, that reprehensible buzzword, "open-world".

With that in mind, I'd pick these as the top five:

1. Wii Sports - obviously
2. Wii Fit - the biggest push for fitness/well-being-based games and opening gaming to other audiences
3. The Elder Scrolls V: Skyrim - popularised the concept of "open world"
4. Brain Age: Train Your Brain in Minutes a Day! - similar to #2
5. Call of Duty 4: Modern Warfare - basically defines the modern shooter

Honorable mentions: Minecraft, Super Mario Galaxy, Dance Central, Assassin's Creed, Braid, Limbo, Super Meat Boy, Dark Souls, The Elder Scrolls IV: Oblivion, Grand Theft Auto IV, New Super Mario Bros. Wii, Uncharted: Drake's Fortune, Just Dance, League of Legends.

There are some other very good games out there, including some others mentioned in this thread, that I don't think are influential. Just because something is good doesn't mean it actually brings about significant change in the way games are made, whereas I feel like I can see some kind of impact that all of the above games had.

For the record, if I were to do a personal top five for the last gen, probably the only game I've mentioned that would make the list is Mario Galaxy.

There's no way to properly describe last gen without Wii Sports. Also, we have to include Guitar Hero to represent all the music games (and dancing games) that spawned from its success.

"Over the period from 2005 to 2008, video game software sales grew by 81 percent, with the music genre accounting for one third of the gain," Pachter said in January. "From 2008 through 2010, software sales declined by 14.9 percent, and the music genre accounted for over 80 percent of the decline."

For the reasons stated above, in no particular order, I would say:

Call of Duty: Modern Warfare

Wii Sports

Guitar Hero

Gears of War

Mass Effect

5 is too restricting. I wanted to include Uncharted because it was able to change the direction of a classic like Tomb Raider, but I had to drop it because more games were influenced by GOW's cover system. Indie games boomed last gen and games like Braid should be listed, but I had to list Mass Effect for the impact it had on other games. So many of them try to include "your choices matter to the outcome of the story" elements now, even the non RPG games

I'll try to make this list as accurate as possible, while not pertaining to my own opinion.

1. Wii Sports (For motion controls)
2. CoD 4: MW (For FPS)
3. TES V: Skyrim (For open-world, action-adventure game)
4. GTA V & Minecraft (Tied for sandbox game)
5. Super Mario Galaxy (For platformer)

FIve? I'll give you ten!

http://gamrconnect.vgchartz.com/thread.php?id=173510&page=1

If you talk about about five games that made the seventh gen, then they are these:

Wii Sports
Wii Fit
New Super Mario Bros.
Call of Duty 4: Modern Warfare
Assassin's Creed

There wouldn't be a seventh gen as we know it without these. This has little to do with whether or not these games are the best, but more with their general (mainstream) impact and influence on the entire generation. Wii Sports at least is indesputable. In fact, if you could only mention a single game to define the last generation, that game would be it. These five lack a role playing game though, which was big during the middle stage, of which I think Elder Scrolls: Oblivion is the most influential. GTAV came too late and despite it's sales I think GTAIV was forgettable for the general mindset of the generation.

Wii Sports
Call of Duty 4: Modern Warfare
Uncharted 2
Gears of War
The Elder Scrolls V: Skyrim

1. Uncharted 2 (Because so many games have tried to replicate this masterpiece. I'm looking at you Tomb Raider)

2. Bioshock (One of the best and most unique experiences I have ever had with a game)

3. Call of Duty 4: MW1 (The game is phenomenal and it started a Call of Duty dynasty that ruled the last generation. But, I personally think it ruined so many others simply because devs have tried to copy the MW formula only to failed miserably.)

4. Mass Effect (Amazing story, absolutely love the characters, and of course the setting, the ME universe is easily one the best if not the best setting in a game that I would love to explore more.

5. Assassin's Creed (The games suck right now but AC2 & Brotherhood where great in their own right and they are the reason I haven't given up on this series yet.)

I don't think I can think of 5 right away since I was largely Wii most of last gen, but I would likely say

Wii Sports - What more needs to be said? It took the game industry by storm and shot Ninten tothe top for a long time and started a trend of motion controlled games, so much so that Sony and MS made their own motion control devices to catch some of the success it brought.

Call of Duty - I feel like COD started the other trend we saw spark in gaming, the FPS craze. I felt like FPS games were so popular in the last gen, which felt like a surge of them were made during this time, and COD lead the charge.

That's all I got. Personally I would also add Mario Galaxy, which really felt like next gen, with its excellent visuals and wonderful music. It was just a sight to see. : )

I will take a different approach and go with the top 5 that defined last gen in Japan
Monster Hunter Portable 2nd G (PSP)
Animal Crossing Wild World (DS)
Brain Age (DS)
Wii Sports (Wii)
... Anyone got a good call for a 5th?? I really didnt want to go with something generic that was big before hand like Pokemon.

Assassin's Creed
Fallout 3
Mass Effect 2
Call of Duty 4
Uncharted