Well I think you need to tell us what type of systems you play on and what games you have already played before because I would say Minecraft but that's pretty much on everything other than the PS3 and I don't know if you have a PS3. I would also say The Legend of Zelda but that's only available on Nintendo Platforms. We can't really answer your question accurately without the correct information. I also don't know if you've already played Minecraft or Zelda.
Everything else I would suggest(in no particular order):
Assassin's Creed series
Fallout 3 and Fallout New Vegas
Fable 2 and Fable 3 (Xbox 360 only)
Trials HD and Trials Evolution (Xbox and PC)
Mass Effect series
Bioshock series
Halo series
Call of Duty series
Plants vs Zombies
The Cave
Don't Starve (PC Only)
Terraria
Grand Theft Auto series
Castle Crashers
Skyrim
The Walking Dead (not survival instinct - the 5 episodes)
Deadlight
Forza Motorsport 4
Batman Arkham Asylum
Bully Scholarship Edition
Battlefield series
The Sims 3
Max Payne series
Portal: Still Alive and Portal 2
Dragon Age: Origins
L.A. Noire
Alan Wake
Comic Jumper
Homefront
Blur
Red Dead Redemption
SKATE series
Borderlands and Borderlands 2
F.E.A.R. series
Condemned: Criminal Origins
Left 4 Dead and Left 4 Dead 2
Saw
Viva Pinata
Saints Row series
Silent Hill series