I thought I'd post a list of games I've completed inspired by my brother's list on his steam page, I've forgotten a lot, I'll try to put a date of completion on most.
Games Completed:
Left 4 dead (2009)
Mirror's Edge (Dec 2009)
Trine (Feb 2010)
Portal (May 2010)
Left 4 Dead 2 (Summer 2010)
Nation Red (Forgot)
Zombie Driver (Nov 2010)
And Yet It Moves (Nov 25th 2010)
Recettear: An Item Shop's Tale (Dec 2010)
Lugaru HD (Dec 22nd 2010)
Battlefield: Bad Company 2 (Dec 25th 2010,)
Plants Vs. Zombies (Dec 26th 2010)
Samorost 2 (Dec 26th 2010)
Shatter (Dec 31st 2010)
Assassins Creed II (Jan 10th 2011)
Bionic Commando: Rearmed [Coop] (Jan19th 2011)
The Wonderful End of the World (19th April 2011)
Portal 2 - Single Player (April 20th 2011)
Portal 2 - Coop - Chun(April 21st 2011)
Magicka - Campaign (Late april 2011)
Magicka - All Challenges to date (May 2011)
Capsized (May 7th 2011)
BEEP (May 9th 2011)
Just Cause 2 (August 15th 2011)
Trine 2 (December 2011 co-op with Brother.)
Stealth Bastard: Tactical Espionage Arsehole (4th Jan 2012)
Serious Sam HD: The Second Encounter (25th Jan 2012)
Jamestown (legendary - co-op) (12th April 2012)
VVVVVV (27th April 2012)
LIMBO (16th May 2012)
Saints Row: The Third (17th May 2012) [Xbox]
Rochard (19th May 2012) [PSN]
Torchlight (23rd May 2012)
Botanicula (29th May 2012)
Cat Poke (28th June 2012)
Command And Conquer 4: Tiberian Twilight (19th July 2012)
Bastion (26th July 2012)
Rock of Ages (15th August 2012)
RUSH (15th August 2012)
Sleeping Dogs (27th August 2012)
Machinarium (30th August 2012)
Starcraft 2: Wings of Liberty (1st September 2012)
Torchlight II (24th September 2012)
Sonic the Hedgehog (25th October 2012)
Gears Of War 2 Coop (18th November 2012) [Xbox 360]
Botanicula (30th November 2012) [ Gog.com ]
Cave Story + (23rd December 2012) [Normal Ending]
The Binding of Isaac: Wrath of the Lamb (26th January 2013)
Sequence (27th January 2013)
Offspring Fling! (2nd February 2013)
They Bleed Pixels (3rd February 2013)
To The Moon (15th February 2013) [ Gog.com ]
A Valley Without Wind 2 (24th February 2013)
Double Dragon: Neon (1st March 2012) [Playstation 3] Coop with Kenny!&
Sid Meier's Civilization V (5th March 2013)
Halo 3 (11th April 2013) [Xbox 360, Coop with brother]
Snapshot (18th May 2013)
Penny Arcade's On The Rain-Slick Precipice Of Darkness 3 (29th July 2013)
Serious Sam 3: BFE (2nd August 2013) [Coop with brother] -I hate CroTeam-
Costume Quest (25th August 2013)
Dead Island (16th September 2013)
Unholy Heights (6th October 2013)
Path of Exile (22nd March 2014)
Lego: Lord of the Rings (27th April 2014)
Guacamelee (19th May 2014)
Brothers: A Tale of Two Sons (15th June 2014)
Fallout: New Vegas (22nd December 2014)
Injustice: Gods Among Us Ultimate Edition (21st June 2015)
Platformines (19th August 2015)
Freedom Planet (26th October 2015)
Far Cry 3 (29th October 2015)
Middle-earth: Shadow of Mordor (1st January 2016)
Metal Gear Rising: Revengeance (29th February 2016)
Alien: Isolation (24th March 2016)
Tomb Raider (28th March 2016)
Batman: Arkham Asylum (25th April 2016)
Victor Vran (27th April 2016)
Dust: An Elysian Tail (22nd May 2016)
Devil May Cry 4: Speciel Edition (13th June 2016)
DMC: Devil May Cry (26th June 2016)
Copoka (1st July 2016)
Remember Me (3rd July 2016)
Oxenfree (31st October 2016)
MASSIVE CHALICE (2nd November 2016)
Darkness 2 (6th December 2016)
Terraria [Expert mode, defeated Moon Lord] (10th January 2017)
Warhammer 40,000: Dawn of War (23rd March 2017)
INSIDE (14th June 2017)
Call of Juarez: Gunslinger (30th June 2017)
Owlboy (10th Feb 2018)
Transistor (24th Feb 2018)
Shank (24th Feb 2018)
Last Day of June (31st March 2018)
Total War: Warhammer II (14th December 2018)
Resident Evil 5 (20th November 2019)
DOOM 2016 (4th April 2020)
Borderlands 3 (23rd April 2020)
Gears Tactics (6th May 2020)
Middle-Earth: Shadow of War (16th May 2020)
DOOM Eternal (18th April 2021)