Help WK with his Backlog!

[Formalhaut]

Steam
Bastion
Half Life 1 and/or 2
Deus Ex
Knights of the Old Republic
Braid

Not much knowledge, but Mr. Carny loved KotOR. I've also heard good things about Braid and Half Life, but they're rather different games, so it depends on what you fancy playing.

PS3
Assassin's Creed IV: Black Falg
Batman: Arkhum City (yes I'm that far behind in the series)
Mass Effect 3 (I have played the earlier entries)
Ni Nu Kuni: Wrath of the White Queen
Uncharted series (I have not played any of them)
3D Dot Game Heroes
Start over/finish Valkyria Chronicles... I know you'll love it WOLF CANOE IF YOU JUST GIVE IT ANOTHER CHANCE!
Same as above but replace VC with White Knight Chronicles
Same as above but replace VC and WKC with Mirror's Edge

Mr. Carny wasn't terribly favourable about Black Flag, thinking the series ended rather neatly on the third game. As for me, I'd recommend Mass Effect 3. Yes, ending blah blah (I personally didn't mind the ending) but everything else about the game is great, and is worth playing regardless if you've played 1 and 2.

I've heard good things about Ni Nu Kuni, and the Uncharted series is a classed PS exclusive (if you have a PS4, you might want to get the Nathan Drake collection). The other games? Not much experience with, so I can't say.

PS2
Beyond Good and Evil
The Bouncer
Digital Devil Saga 1 and 2
Drakengard
GTA: Vice City
Godhand
Killer 7
Shadow Hearts 1 and/or 2
Steambot Chronicles
Tales of the Abyss
Yakuza
Zone of the Enders 2nd Runner

GTA: Vice City is a very solid classic from this era, and if you've enjoyed other GTA games, it is worth playing. Not much knowledge of the others, frankly.

PlayStation
Arc the Lad III
Parasite Eve
Finish Saga Frontier II
Finish one of my playthroughs...

I've heard of Parasite Eve, which is something. Other than that, I've got nothing.

PSP
Prinny: Can I really be the hero?
Loco Roco
Tactics Ogre: Let Us Cling Together
Assassin's Creed:Bloodlines
Finish P3P or Star Ocean 1

I'd recommend finishing P3P if you've never beaten either the Male or Female stories. If you've beaten only the Male one, then finishing the Female route is also recommended.

Tactics Ogre is good, from what I hear.

N64
LoZ: Majora's Mask

Majora's Mask is a classic, really. Well worth playing.

3DS
Bravely Default (Once you finish 4 Heroes of Light)
Persona Q
Soul Hackers

I'm playing Persona Q now. It's by no means the best Persona/SMT game ever, but it is good, and pays good tribute to the characters. Yes, they're flanderised somewhat, but it is interesting watching the two sets of characters interact, and the story is surprisingly interesting.

Bravely Default is obviously well known about. If you don't fancy PQ, then that's also decent.

DS
LoZ: Spirit Tracks
Rhaspsody: A Musical Adventure
Finish one of the half dozen games you started... like Revenant Wings or DQIX.

I've played Spirit Tracks and it's a decent Zelda game. Nothing truly special about it, though there are some interesting puzzles involving the use of Zelda's spirit.

GameBoy/Advance
DemiKids Light and/or Dark Edition
Pokemon Silver
Mega Man Xtreme

Pokemon Silver is often seen as the best Pokemon game, so it is a good call to play it.