I just platinum'd FFX HD and it took me 120 hours!

Are MMORPG's cheating? :p If not then FF14:ARR. I've put a bit under 1400 hours into it, with the core 2.0 story taking me about 190 hours (though that includes some messing around with other classes and crafting).

If you're excluding MMO's then i'm not sure which would be the actual longest, but I've probably put the most time into either FF9, Pokemon Emerald or Persona 4. Not sure which though, i only developed the habit of timing game sessions a few years ago (though i know i spent 114 hours with P4:G).

Now go platinum Star Ocean 4! I was considering doing it myself a few months back, but the guide says it takes 450 to 1000+ hours. Bugger that :p

81 hours on Dragon Age: Inquisition. Although I'm confident my playtime for Persona 4 Golden will surpass that.

Fallout 3

The best western rpg ever made.

If we're talking about just beating the story then it would be P4G for me. It took me a little over 90 hours.

EW WTH no!! I hate Star Ocean 4!!!

But wow that amount of time is hardcore. The worst part is when you have to do more than one playthroughs. That would turn me off!

Like beat the game start to finish? It took me 124 hours to platinum Skyrim, otherwise my 100% run or very close to it of Final Fantasy IX and Tactics took a long time to do.

Actually, Dragon Warrior 7 is one of them, although it doesn't take 100 hours unless you're going to do everything, and even then it's under 100 hours.  I think I finished the game with most everything completed in 60-70.  Haven't finished everything else up yet, but my save data is sitting at 80 hours with just the secret area I need to complete.  I've also captured some, but I think capturing every monster in the game for the monster farm might push it beyond 100 hours.

Depends though, because it could also be Tactics Ogre.  First time playing through Tactics Ogre and completing everything, including Hell's Gate, all characters at 50, all rare equipment, a few Liches and Hydra's, etc, took me 80 hours, but that didn't include any of the other paths, and there are three paths in Tactics Ogre, so technically you could say the game is around 100-120 hours to complete if you talk seeing all of the main story alone.  Tip for anyone interested getting super OP angels.  Recruit them in the battle with Bishop Branta and they'll have the best stats you can get withoutusing the Necro/Rebirth trick or using stat enhancers.

I've also played Dragon's Crown for 180 hours.  So would that be considered the longest.  :P.  The Labyrinth of Chaos is 100 floors with three randomized maps each.  Mirage Tower might have more.  I've gotten to Ultimate difficulty with every class.  One of my favorite games of last gen.

I'm also playing Fantasy Life on my 3DS and right now I have 40 hours, which is only going to go up.   It's basically White Knight Chronicles 2 meets Animal Crossing meets Secret of Mana. 

Star Ocean 4. I did not play it, but it took over 200 hours to beat the ethereal queen.