For me, 2008.

GTAIV, Left 4 Dead, Prince of Persia, Fable II, Fallout 3, Viva Pinata TIP, MKVSDC

2010.

Mario Galaxy 2, Bayonetta, Mass Effect 2, Monster Hunter Tri, Sin & Punishment 2, Donkey Kong Country Returns...

2007 hands down
Super Mario Galaxy
The Orange Box
Bioshock
Modern Warfare
Halo 3
Elder Scrolls: Oblivion
Mass Effect 1
Final Fantasy VI Advance
Persona 3
Ghost Recon 2
PGR4
Zack and Wiki
Castlevania Dracula X Chronicles
Witcher 1
Test Drive Unlimited 1
All Pro Football (even though it wasn't as good as NFL2k series, it was nice to get another game)

2008 was pretty damn good and 2010 was not bad. So far this year seems like the worst in a long, long time.

2007

Halo 3
Mass Effect
Call of Duty 4: Modern Warfare
Assassin's Creed
Bioshock
Resident Evil 4: Wii Edition
Metroid Prime 3: Corruption
Super Mario Galaxy
Uncharted: Drake's Fortune
Ninja Gaiden Sigma
God of War II

It's a tough one between 2008 and 2010. I'm from the U.K, so I'm counting European release dates. I'm also not counting any ports/remakes.

2008 saw:

Super Smash Bros Brawl
Mario Kart Wii
The World Ends With You
Metal Gear Solid 4
Little Big Planet
Final Fantasy Tactics A2


2010 saw:

Super Mario Galaxy 2
Rune Factory Frontier
Final Fantasy XIII
Dragon Quest IX
Donkey Kong Country Returns
Bioshock 2
Tatsunoko vs Capcom



It's worth noting however, that most of 2008's great games were concentrated in the first half of the year, by the end of June all the games I listed, with the exceptions of LBP and FFTA2 had been released. 2010's were far more spread out. Early 2008 was IMO easily better than any other similar length period in gaming, but as a year it is very hard to choose.

2010:

- Donkey Kong Country Returns
- FFXIII
- Kingdom Hearts : Birth By Sleep
- ME2
- DQIX
- SMG2
- NIER
- RDR
- 999
- Just Cause 2
- GT5
- MGS Peace Walker
- Persona 3 Portable
- Yakuza 3
 - Warioware DIY   
- Star Ocean 4 PS3 Release

*explodes*

2008 is 2nd! (SSBB, MGS4 and err LBP)

I think with each year games and consoles just get better and better, the best is still yet to come.!!

2007 methinks

Two-thousand-ten.

2010 was a great year for every console and it might have my best gaming year ever, as I not only played the games which were released during said year (SMG2, Heavy Rain, GoW3, DKCR, Red Dead Redemption, Mass Effect 2, FFXIII, Just Cause 2, to name a few) but also many HD jewels I had missed and other Bioware games from previous years I played on my new PC (Mass Effect Saga and DAO basically).