Topic: Notable Game Series You Haven't Played

Mass Effect comes to mind some others are

Sly Cooper
Jax and Daxter
Rachet and Clank
God of War
Call of Duty
And a tons more that I am forgetting.

I have a lot of shame when it comes to the big franchises I haven't bothered with. Here is the short list:
God of War
Battlefield (played a bit of Battlefield 3 and just didn't get on with it at all)
Dragon Age series
Pikmin series
Paper Mario series
Twisted Metal games
EA Sports games
Batman Arkham games
There are more that I am forgetting but I really need to get on it and play some of these games.

Woah you missed alot of great franchises especially the Batman and Paper Mario games.

The only one of these that I can think of, which has certainly been pointed out to me, is the Bioshock series.

@Maximus_T - wow! How come you missed that? Needs to be rectified immediately. Grab yourself a cheap pre-owned copy of Bioshock (1) at your local game store and enjoy one of the seminal shooters of recent years. The other two in the series I will leave up to you - IMHO they each had their merits but weren't as strong.

As for me the series I have never played are Playstation/Nintendo specific:

Resistance - played the first with my brother on his PS3 then went off to university and brought an Xbox...I make no apologies
Killzone
Batman Arkham - caveat, I have 2/3 but never had the time to sit through them, I really use them as filler between big launches
Sly-Cooper
Smash-Bros

Sinners! All of you!...And I am among them. Namely, all the great PS3 exclusives I missed when I jumped ship to Xbox.

Bioshock
Elder Scrolls
Fallout
Dead Space
Red Dead
NBA 2K
Mass Effect
Left 4 Dead
Half-Life
Battlefield
Medal of Honor
Call of Duty
Shenmue
Yakuza
Animal Crossing
Pokemon

to name a few.

• Advance Wars
• Altered Beast
• Bayonetta
• Bioshock
• Chibi-Robo
• Crackdown
• Dark/Demon Souls
• Darkstalkers
• Dead Rising
• Devil May Cry
• Elder Scrolls
• Etrian Odyssey
• Fable
• Fallout
• Gears of War
• God of War
• Guilty Gear
• Half-Life
• Halo
• Killer Instinct
• Killzone
• Last of Us, the
• Left 4 Dead
• Mass Effect
• Panzer Dragoon
• Pikmin
• Professor Layton
• Rachet & Clank
• Shadow of the Colossus
• Shenmue
• Shin Megami Tensei
• Sly Cooper
• Streets of Rage
• Virtua Fighter

Okay, okay, I think I'm gonna have to stop before I go overboard. You just don't realize how much you miss unless you really stop to think about it. Developers could stop making games today, and there'd be more than enough great games for any one person to ever get through, lol.

Resident Evil: I'll have to get around to playing one of these games someday.
Silent Hill: Another series I'll have to eventually try.
Mortal Kombat: Don't care much for fighting games.
Pretty much every PC point and click series: I did try Maniac Mansion once but wasn't impressed. Those types of games are the ones where I would by relying on Gamefaqs too much... no thanks.
Any notable PC RTS: These types of games just seem too complicated for me.
The Sims: Think I'll just stick with Animal Crossing.
Gears of War: Don't care for shooters.
Half-Life: Same as above.
Battlefield: Same as above.
Mass Effect: This one just doesn't look like my cup of tea.
The Witcher: Yet another series I'll have to play eventually.

There's more, but those are most of the more popular ones.

Quite embarrassingly...Metal Gear Solid! Never once touched any of the games!

I've also never played anything by Bethesda.