Perfect Game

Completely finished DayZ with people not shooting others on sight.
Or... Payday (robbing) + receiver (realistic guns) + ARMA (realistic, billion key bindings)

There is nothing even close to perfection. You can say that this game is excellent, fantastic or awesome. But you can never say this game is perfect. The word "perfect" is far beyond this world.

There were many games which were very close to perfect (e.g. Planescape Torment, Diablo II LOD), but all of them had at least one flaw. If you're looking for the best of the best, however, then check the "Top 100 Games of All Time" lists.

Nothing is perfect, but Kingdom Hearts-series and Metal Gear-series go really close!

Story wise? Telltale games or Quantic dream.

Bugs? well I haven't seen any bugs on super hexagon :P

There is no such thing as a perfect game.

Bubble Bobble, played it for the first time nearly 30 years ago and still love it. Sounds like a perfect game to me

The two games (for me, obviously) that came close to "perfect" would be Half-Life 1 and Fable: The Lost Chapters.
Edit: Also Warcraft III with Frozen Throne.

Skyrim and The Witcher 2 for me.

Homeworld: Cataclysm

tetris. the most perfect and hardest game i ever think.

Fallout 1.

Super Mario Bros 3

Tied between Oblivion & San Andreas.

first Metal Gear Solid game was in my opinion the closest one to be called perfect. There's simply not a single bad thing i could say about it.

Just today I played Wipeout HD on my PS3 and thought:
This game is way ahead of its time. It's perfect.
I must admit it's very very hard, but that's a fault on my end.
The design is beautiful, the graphics (1080p, 60 fps on an early PS3 title), the music, the goddamn menus are excellent... Makes me sad Studio Liverpool was closed. Perhaps Firesprite studios will pick Wipeout up again.

minesweeper

Far Cry 3 is probably as close as a game has gotten to perfection in my opinion.

Deus ex series

Braid...?

Skyrim'ish type of huge open world with books, lore and amazing vistas. Steampunk setting. Mix of decent action and tactical combat. RPG kind of perks and stats affecting gameplay. Multiplayer, not MMO, but at least 32 slots. Long and well-written plot. MOD SUPPORT. Bf4-like commander mode, but featuring a tabletop-style Game Master capable of adding foes, changing rules and balance, setting dynamic events etc. Decent, deep, indie-quality minigames. Lots of stat-based loot. Challenging puzzles and platforming sequences (leading to premium bonus content, but not mandatory). And most importantly, challenge (tough quests, no auto-adjustment of loot and enemies, tough enemies really hard to kill, premium loot and rewards requiring real skill, thought and teamwork to get. Quests that you can actually and permanently screw up if you're not careful with the way you do stuff and talk to NPCs). Vehicles and decent driving mechanics.

Hopefully in my lifetime. But not too soon. I want to spend my retirement playing this.

Grim Fandango.

Pokemon/thread.

Pindball perfect game, because nothing can be added there :D