Normally i do these lists least recommended to most, but not this time. Why?
...i only keep the top six consistent... anyway:
#1: Portal
The closest thing to a flawless game in existence, it's a nice three hour puzzle run with a slew of interesting physics puzzles and some of the funniest dark humor you will ever hear in a game. Definitely something to play when you're about to be put into a chemically induced coma you may never wake up from.
#2: Shadow of the Colossus
The most beautiful example of minimalist storytelling and letting the environment and atmosphere speak for the game, Shadow of the Colossus is one of the most definitive examples of games as art. Plus, leaping off of a speeding horse and grabbing onto a low-flying snake to stab it in it's weak spot, all with manual controls instead of QTEs makes you really feel a sense of accomplishment.
#3: Silent Hill 2
The greatest horror experience ever, it has excellent pacing and the monsters are made the more frightening in that their grotesque image bear symbolic significance that you often recognize subconsciously. It focuses on a sense of isolation as nothing around you seems to be totally alive, and the feeling of helplessness added by an invincible boss adds to the experience, while the story of James is such an unbelievably deep tale of despair that at the end of it al you feel so emotionally drained it's like your brain just had a guilty orgasm.
#4: BioShock
Probably one of the best examples of story telling in a game and possibly the ONLY good example of in medias res storytelling in games period, BioShock has entertaining gameplay that is only let down by the hacking mini-game and the fact that you can break the difficulty curve with the proper use of the research camera, plasmids, and gene tonics.
#5: Fallout 3
An FPS/RPG with an insane amount of content and that has a moral choice system that is more than just good, bad, or evil. The fact that it gives a real effort (It doesn't succeed mind) to make the villains come off as not evil just for the sake of being evil but are actually victims trapped in the past of a war that destroyed the world is also a nice touch.
#6: Half-Life 2
Valve's great masterpiece, and the single best pure-FPS with absolutely no competition since unlike Halo or CoD Half-Life has good pacing, characters, and doesn't need a stupid cop-out like "BUT THE MULTIPLAYER," the only reason it's low on this list is because while it is an excellent FPS, it is a little on the short side, and Valve is extremely slow in releasing the episodic extensions to the game.
#7: Grand Theft Auto IV
A fun third person sandbox game that has cover based shooting and an advanced enough A.I to make it all viable while at the same time no regenerating health to make it hopelessly easy, while at the same time cheats to help the worthless bastards who were made soft by years of games with infinite, regenerating health. Some people mind find that the story is a little overwritten for a game that most people will go through casually murdering NPCs when they're bored, but i actually like it where the main character comes off as an anti-hero, and you actually understand how he came to be that way.
#8: God of War
While the gameplay lacked some of the polish of God of War II and III, the original was the best because it had some nice challenges and an interesting Greek tragedy storyline. Though the balance wasn't perfect, the Army of Hades magic broke the curve somewhat.
#9: Prince of Persia: Sands of Time
Insanely fun precision platforming that is tricky due to just how perfect your timing needs to be but not frustrating because of the ability to rewind time. Combat may be subpar but the characters are very interesting.
#10: Hitman: Blood Money
A fun little free-roaming stealth action game where countless options are laid before you to get the job done. It's far from perfect, the A.I and environments needed a lot of polish, but more linear stealth games where killing enemies is often your only option aren't that interesting. It's more fun to feel like you're a really smart guy when you are hiding in plain sight and kill someone with what looks like a tragic accident.