I probably haven't played most highly acclaimed games, and at this point I'm not going to try. If I mention any of them someone will go on and tell me I must play them, so might as well not say anything.

I hope I'll finish KOTOR this year, and I will probably finish The Blackwell Epiphany. That would be good enough for me.

just to name a few: GTA IV and V, Starcraft, WoW(the mmo ones, i played the rts ones from the early days), any Witcher, any Diablo, any Fallout, any Assassins Creed .... i could go on, hehe

I've never played the Mass Effect games, either. I own all three of them. Bought the three pack in the 2013 Christmas sales for like $10 or whatever. Figured I'd give them a shot. Silly me I didn't do my research beforehand so it wasn't until afterwards that I discovered the $100 or so of DLC between 2/3, many of which apparently really "complete" the game. I refuse to pay that much for DLC for games that old (which apparently never goes on sale for PC) and I also refuse to bother to start playing it until I have everything, or least the bigger expansions. I just decided no Mass Effect until that the DLC drops in price.

Well... Skip the credits and you won't have to hear it ;)

She is. But she only annoys you before and after a puzzle. Gameplay is fine.

The WHAT??? I haven't seen anything of geekchicwhatever in Portal. Play the game and ignore the internet. Makes even most of those horrible, unplayable and PC-unworthy, bad console ports enjoyable (because without the interwebz, you won't notice that they're bad console ports).

The cake used to be a lie, but then it took an arrow to its knee.

I never got to play the orignal Xcom series. So I bought Xenonauts here to compensate, but I still haven't gotten into it.
Tons of old lucas arts titles, as I didn't have a PC for it at the time. I did get to play Monkey Island games later on, but only the remastered version.
Ultima and M&M games. No real reason, I own them here but I can't put myself to play them. I did get M&M 9 back in the day, thinking I'd try the series, and didn't like it at all, but apparently it's a poor choice.
And ANY flight simulators or racing games. Unless you count Carmaggeddon, I did play that. Anything I can do to help on that front?

The DLC is pretty ridiculous and my main complaint, but I don't agree that they are necessary in any way. The Extended Cut one, maybe, but it's free. You're missing out on a pretty fun series!

yup, but I can understand the idea of not wanting to play the less complete version. Time is valuable, and so while I enjoyed the standard Shadowrun: Dragonfall campaign, had I known there was going to be an extended cut I would have held back on playing until that one was out. I typically don't have the time to play the same game twice (can't play every game once, as this thread proves), and so I'd rather play the full one the first time.

List too long. some just played briefly or too little

Dragon Age series
Mass Effect series
Assassin's Creed series
Battlefield series
Total War series
Call of Duty series
Halo series
Far Cry series
Diablo 3 reaper of souls
Starcraft 2 Heart of the swarm
Fallout 1,2 and Tactics, new vegas
System Shock series
Wasteland series
divinity series up to Divinity:OS
Homeworld series
God of war series
Deus Ex series
Wing commander series
Oblivion series
Monkey Island
Bayonetta series
Planscape torment
Icewind dale series
Mount & Blade series
World of warcaraft
Witcher series
Never Winter night series
Shadow Run series
Grim Fandango
X-wing
Banner Sage
AI War series
Don't Starve
Jagged Alliance series
Legancy of kain series
Ultima Series
Thief series
Hitman series
Sim city series
FTL
Temple of element evil
I tire......

Too many to keep track of them :(

Lair of the Shadow Broker and The Arrival are two pretty important ME2 DLC. When you meet Liara without having Lair of the Shadow Broker installed, you'll notice that something is missing. And certain things in ME3 are a direct consequence of this DLC too (some references during the mission "where you pick up someone from a STG base" won't make any sense either)! The Arrival sucks, but it is what happens between ME2 and ME3. I haven't played ME3 without an imported character (who didn't do this DLC), but I can't imagine how it starts without the things that happened there. So, yes, you can play ME2 without DLC. But your ME3 experience will suffer from this.

Some DLC in ME3 are even more important. From Ashes and Leviathan should've been part of the base game, since they reveal lots of things about the Protheans (From Ashes) and the Reapers (Leviathan) - you know, the two species that form a major part of the main story ;)

As some others stated. Too many to name that I haven't gotten around to playing. I just don't have the time like I used to back in the day where I was never interrupted and could play a game for hours on end.

My list of shame - Planescape Torment, Balder Gate series, NWN series, Portal series, Grim Fandango, Tie Fighter/X-wing series, Deux Ex/ System Shock 2, Civiliaztion series, and a couple more I can't think of at the moment. I won't even get into console game list =P

Happily I can say so far I've finally gotten around to working on the Blackwell games which has been in my library for a few years =P A little bit of progress as I did finish the first game last week or so.

Convince me it should move higher up the priority queue? Currently it's after Diablo and Teenagent, but only because the latter is supposedly very short.

The only thing that should come before Diablo is breathing, and I'm not even totally sure about that.

I played without most of those and still enjoyed myself, but I guess I'm not much of a completionist when it comes down to it. I only had Lair of the Shadow Broker, which I recommend if anyone is going to buy any DLC. They do give background as to why Shepard is in the situation he/she is in at the beginning of ME3, even if you don't have Arrival.