Honorable Mentions include: Mass Effect Trilogy, Vanquish, Minecraft X360, NHL 2K10, Burnout Paradise, Left 4 Dead 2 and Rock Band 3.
1. Fallout 3
Fallout 3 is another Bethesda masterpiece with a really enjoyable world to explore. You can get lost in the game for 100's of hours and with the excellent DLC add-ons you get even more to discover.
LOOT is Awesome, but, it is even more awesome when it is GUNS! I can find a never before seen gun every single new game and with 4 player co-op you really can't go wrong. I also love the game's art style and the fact it doesn't take itself too seriously. Fun DLC (except Mad Moxxie) help change up the scenery. Oh, also, Clap-Trap. Nearly 300 hours of gameplay time over multiple characters and fairly frequent play for 3 years round out this choice.
3. Call of Duty 4: Modern Warfare
The sad thing is I'll probably never play this again because I am basically done with the Call of Duty series but this game got me hooked on FPS games and FPS multiplayer. I spent over 384 HOURS playing this. Unfortunately the series was never able to capture me like this title did back in late 2007 when I gave it my Game of the Year in the 11th hour.
4. The Elder Scrolls V: Skyrim
I've played only 2 characters in Skyrim one has over 130 hours on it and the other has nearly 200 alone... But get this, I have never completed the main quest with either of them. Amazing graphics and another fun to explore Bethesda world means I stay hooked for 100's of hours.
5. Battlefield 3
Epic battles. Good Teamwork. MINIMAL LAG. Battlefield 3 is fun to play because it has such a different feel from the LONE WOLF mentality of the Call of Duty games. As a bonus the game's dedicated servers make for excellent and EVENLY MATCHED gun battles which mitigates a major issue of online multiplayer.
6. Saints Row 2
WHA? Not GTA IV? Nope, I enjoy the Saints Row games and the second game is bigger, better and the most feature packed of them all. There are easily 60+ hours of gameplay here if you want to challenge yourself to do it all. It's a perfect feature packed sequel, unlike the streamlined as hell Saints Row: The Third.
7. The Elder Scrolls IV: Oblivion
Oblivion has some problems that border on serious, for example the leveling system actually works against you... but I still enjoyed it through multiple characters for probably over 400 hours and that says a lot when a game can overcome its problems and still be enjoyable for that long.
8. Portal 2
It's replayability factor is a little low because of the puzzle like nature of the levels which puts it lower on this list, but Portal 2 is a great can't miss experience. From the mind bending puzzles to the laugh out loud humor everything is done excellently. It's also like you are getting 2 games in one with the separate Single Player and Co-Op levels.
9. Forza Motorsport 2
I'm just going to put it this way... I hadn't been this into a sim-racing game since Gran Turismo 2 way back in 1999. I 100% completed the career mode, which took over 50 hours alone and played tons of online races. The sequels were never able to capture the same magic... in fact I haven't even played Forza 4.
10. Prince of Persia
This is the surprise of the bunch I am sure. If it wasn't for the fact that Fallout 3 also came out in 2008 I think it would have likely been my game of the year. I loved the simplistic and relaxing gameplay in which you couldn't "die", the combo based fighting and I loved the way the Prince and Elika interacted during the course of the game. To the chagrin of some, I kind of wish the PoP series kept going in this direction.
So there you have it 10 of my favorite games from this console generation so far. I'll probably come back to this list whenever the new systems come out and make it more definitive but for now I think it gives you a good idea of the games that I have enjoyed in the last 6 or 7 years. I'll be back in a few days or so with 10 Cool Boss Fights I Could Remember (yes, that is the title). So look forward to that. Loading Complete!