If we set "This Generation" as being roughly 2006-Present, I'd say my top five would be:
1-Alpha Protocol (2010): I really love this game. There are plenty of criticisms I could throw at it, but when all's said and done, it has provided me with an incredibly fun and immersive experience on every playthrough (and I've played through the whole thing eight or nine times and enjoyed each time). Also, it's wonderfully refreshing to get an RPG set in something other than D&D style medieval fantasy. There are so many great settings for an RPG, yet 98% of the CRPGs we get cluster in the same D&D paradigm. It's great to see a triple A level RPG actually take a risk and do something new.
2-Mass Effect 2 (2010): While the nuclear powered trainwreck that was ME3 has killed off most of my interest in the series, Mass Effect 2 was a game that I really loved. Like Alpha Protocol, it has its short-comings, but they are all eclipsed by the way the game made me feel like I was living in this rich, intriguing Sci-Fi universe. Running through the smoky, dingy, crime-infused, hell-hole of Omega; wandering across the starkly luxurious corporate hub of Illium, every inch whispering of sinister intrigues; Seeing the blasted, post-apocalyptic nightmare-land that the Krogan had made out of Tuchanka; fighting mercenaries on remote, barely charted worlds; Fighting Geth under the shield-frying radiation of a dying sun; all of these locales were so wonderfully evocative, and crafted so expertly, that I became completely immersed in the game. Also, its large cast of characters insured that we got to learn about this universe through many diverse viewpoints. All-in-all, it's the kind of game I would really like to see more of. Unfortunately, playing it now just makes me think about ME3, which makes it hard to enjoy myself, but hopefully that will pass with time.
3-Mask of the Betrayer (2007): I'm not sure if this really counts as "Of this generation" as it stylistically is most similar to the previous generation (e.g. the KotOR games, Jade Empire, Neverwinter Nights), but as it is chronologically part of this generation, I'm counting it. While I did greatly enjoy Neverwinter Nights 2, MotB is on a whole other level. Even with the anticlimactic ending, it still managed to drag me into an immersive and thought provoking experience. As clunky as the spirit-eater mechanic was, it really brought the "being cursed" sensation to life (unlike, say, the Bhaalspawn thing in the BG games). Rarely have I been as connected to my character's experience as when I finally arrived for the final siege, our mage out of spells, all of us exhausted since no one in party had slept in days, but pumped for the battle that would end this. That was the most epic battle I've ever fought. I've seen battles in games that were presented as more epic, but this one actually was epic due to the way the game had led up to it. While overall, MotB is a clunky game, there are enough brilliant aspects to it, that it deserves a spot on the list.
4-Deus Ex: Human Revolution (2011): It took me a while to get into this game. The first time through, I was playing as a non-lethal, stealth expert. As such, I got steam-rolled in the first boss fight. I un-installed the game, and didn't pick it up again for at least a year. When I finally tried it again a few months back, I rolled a combat-spec character, and ended up loving the game. I loved the way the game actually made me grapple intellectually with the issue of human augmentation. My initial stance was, "I wouldn't do it, but it's other people's right to do what they want to their bodies". As such, I thought the controversy of it was stupid. But as the game progressed, it did a great job of showing all the complications that could arise a result of the technology. People being unable to get a job unless they cut their arms off and replace them with fake ones, which will mean that they will then become dependent on expensive pharmaceuticals, and their inability to pay for these drugs will leave them as virtual slaves to the corporations that forced them to get the augs. I love it when a story can change my preconceptions about an issue, and this game did so. I also liked the level design. The devs did a great job of recreating the original game's non-linear levels. Too bad the shitty boss fights are completely incongruous with the rest of the design.
5-Fallout: New Vegas (2010): While I enjoyed Fallout 3, it never felt very Fallout-y to me, and after my first play-through, I've never really had the urge to play it again. Fallout: New Vegas fixes this. It feels so much like a Fallout game that it actually made Fallout 3 look bad in comparison. While the main plot is a bit underwhelming, that's pretty much par for the course for Fallout games. Where the series shines is the freedom it gives you to wander around doing random quests and interacting with the inhabitants of the post-nuclear world, and Fallout:NV is no exception.
Games That Didn't Make the Cut:
Dragon Age: Origins - The origin stories and the political intrigue were cool. The multiple ways the ending could go down were really well done and are a great example of how to end an RPG right. Unfortunately, everything between the good bits was a tedious slog through mind-numbingly boring battle after mind-numbingly boring battle, and none of the companions particularly interested me, except maybe Allister. As such, I find it difficult to replay the game, despite its merits, as the bad parts are just too long. I feel like I'm wasting my life slogging through dull combat after dull combat trying to get to the good parts.
Dragon Age: Awakening - similar to DA:O. Boring combat, too many encounters to slog through between plot moments. Still, the moments of political intrigue were engaging enough to make the game worthwhile, and the companions were more interesting than in DA:O.
Dragon Age II - My favorite of the series. Combat still blows, but at least you get it over with a bit faster. Where the game shines is in making the world feel interesting. The first two games felt bland and generic, but DAII's world actually has vibrancy and character. I really enjoyed the city of Kirkwall, and I liked all of the party members in the game. The game really goes downhill in the third act, though, and there's still the disconnect from the earlier games where the templars don't seem to notice if you run around the city with a party full of apostate mages who are blatantly throwing magic everywhere.
Mass Effect: Has some great moments, but gets dull after several play throughs. Its world isn't nearly as immersive as ME2's, nor are the companions as interesting.
Mass Effect 3: The short comings of this game have been discussed to death, no need to dredge that up here. Suffice to say, I did not care for 80% of it, and the 20% that I did like wasn't enough to make up for the crippling deficiencies in the other 80.
The Witcher - I enjoyed the combat, and some of the political intrigue was actually pretty engaging. For a while, the game had me feeling like I really was getting caught up in these political machinations that I desperately wanted to avoid but couldn't, which was great. That said, I didn't give a shit about any of the characters, including Geralt, and towards the end, they kept interrupting the action every 30 seconds with a completely unnecessary cut scene of some bad-guys showing up or rocks falling or whatever, which murdered the pacing. Overall, a decent game but not one I want to replay.
The Witcher II - Like the Witcher, there was some interesting political stuff going on. Unlike the Witcher, the combat sucked, which combined with the unlikeable characters, meant that I never finished the game.
*EDIT* Fixed some typos and added ME1 and 3 to the list at the end
