God Hand is a good candidate. To unlock everything you have to beat the game without using the god hand and roulettes.

Completing Star Ocean games takes forever as well.

Edit - These are some trophies for Star Ocean 3 (300 trophies in total):

50,000 Battles

Defeat Ethereal Queen at Universe Without Taking Damage

Defeat Freya at 4D Without Taking Damage

Defeat Lenneth at 4D Within 20 Minutes

Defeat Luther (final boss) at Lv 1

Defeat Luther at 4D at Lv 10

Defeat Lenneth Using Only Metal Pipe

(4D and Universe are difficulty settings)

Ghost 'n' Goblins

What about Gears of War 3? I heared it has a particulary fiendish achievement for the Multiplayer, don't know any details though.

Warhawk. A game where the trophies are all based on online play is near impossible for me to platinum. Cause everybody plays so random you'll never know when you'll have the opportunity to achieve it.

Just like TF2 then. Post a video that recieves 100k klicks my ass :D

Well based on what I own that honor belongs to Ninja Gaiden Sigma 2. The team missions are INSANE! Two main groups of enemies imo ... waves of super tough enemies and sometimes crappy servers. :/

I'm planning to get Demon's Souls soon and I heard it is incredibly difficult, but since I have never played it I can't say.

I heard there was one Final Fantasy game that hasn't been 100%ed yet on Xbox live because the final achievement (every skill/class maxed out on every character or something) is basically impossible

o.O that's insane. Could it be FFXI, the MMO?

Even if you know what you are doing you have to beat Demons Souls like 3 times to unlock everything on one character. Also, there's an item that you can only get like 3 times per playthrough from a fleeing lizard to upgrade your weapon. I think it was the moonstone. If you don't catch the lizard and /or the item doesn't drop you are essentially screwed for this run since the lizard doesn't respawn and the game saves permanently, like Diablo 2. I heard there is an exploit to farm the lizard but I don't do exploits/duping. Needless to say, I don't have the game at 100%. No idea about Dark Souls though, I'm only halfway.

Not sure, it was in the Gaming World Records book - I'll have to see if I can find it