1. The Witcher 2: Assassins of Kings
The writing in this series (and the novels it's based on) is so good it will make you retroactively hate the writing in other games you've played. They have seriously ruined bioware games for me. I played this game as a nice guy for about half the game. I even spared someone who tried to double-cross me and generally let people go when it gave me the option. By the end of the game I was so wrapped up in the plot and angry about certain events I just started murdering all the nastier characters I could, consequences be damned.
I really liked the difficult nature of the combat as well; they pretty much force you to use all your abilities from moment one. Great story, gameplay, visuals, voice acting, it's as complete as packages come.
2. Batman: Arkham City
Batman has the most enjoyable fist fighting and stealth sequences I've ever played in a game. During predator sequences you are exactly that, a predator. The city traversal takes a little getting used to, but once you do it's fast and fun.
If you get tired of it just be the goddamned batman and go dive bomb the nearest group of thugs. All the gameplay is incredibly satisfying as is the conclusion of the story, a rare feat for a game.
3. Saints Row: The Third
You should play Saints Row.
4. Dark Souls
This game is all about patience, careful exploration, and really fun weapons. The multi-player is fun and unique too when you actually get summoned. That unfortunately happens a lot less than in Demon's Souls.
Still, Nothing beats the feeling when you finally conquer a hard boss, or help someone else conquer that hard boss, or when you smack a large monster to the ground with a 2-hander, or when you discover Ash Lake for the first time.
5. The Elder Scrolls V: Skyrim
Skyrim has incredible scope, but the actual gameplay is not up to the standards of the rest of the games on this list. I also got tired of fighting draugr by about the third crypt I had been into (you will fight A LOT of draugr). That said, they've improved everything over Oblivion and this is the longest I have ever played an unmodded bethesda game. I am really looking foward to what the modding community will come up with to fix the enemy variety.
6. Deus Ex: Human Revolution
This game was such a pleasant surprise when I played it. Almost everything about it is quite solid and lives up to the name. I only wish the voice acting and endings had been better, but I guess those flaws also live up to the deus ex name.
If anyone out there is having trouble with the bosses, your talents don't actually matter that much. The only combat talent that helps with bosses is the damage reduction talent (or is it a health boost? I forget) Anyway, all you need is a grenade and a moderately upgraded shotgun. Or maybe just a lot of grenades. Start with a grenade and then run up and shotgun them in the face while they are stunned. They should die before they recover, I killed all the tyrant bosses this way. Don't let those boss fights ruin the game for you this method ends the fight in seconds.
7. L.A. Noire
I really hope this type of game becomes the future of adventure games.
8. Portal 2
Portal 2 has some really funny dialogue and satisfying puzzles, especially in co-op mode. I felt like a damn genius when I solved a particular one involving some mid-air physics.
Everything about this game is beautiful.
10. Dead Island
The game is pretty fun on your own, but the real fun is in the co-op. How much fun you have will depend on the quality of your friends, but I had a damn good time just playing with my girlfriend who can't really play games and randoms on the PC.