So, in my bored state late last night, I started to compile a list of every game we know will be, or at least has a possibility of being at E3 in some capacity, and the list just kept growing. In fact, I'm sure I'm forgetting some, so if anyone thinks of any other be sure to say so and i' ll update it. This is a list of games possibly at the show by the way, not games shown on the press conferences. This list is also a good way to have an idea of what games will come out in the next year and half. Let's get this started then.
 
MICROSOFT
 
Confirmed
 
Gears Of War 3 
Halo Reach 
Fable 3 
Crackdown 2
XCOM
The Secret World
Ninety Nine Nights 2
Virtual On Force (recently confirmed to be the Sega game in development, it's still sketchy if its exclusive or not, but for now it is. It's also more of a TGS than E3 game, but we'll see)
Portal 2 (I'm pretty sure I saw somewhere, the GI cover maybe, that it was 360 and PC exclusive, but if not, let me know)
Comic Jumper XBLA
Risk Factions XBLA
Limbo XBLA 
Hydro Thunder Hurricane XBLA
Monday Night Combat XBLA
Hydrophobia XBLA 
 
Speculative
 
Mass Effect 3 (we know its in development, the question is, is it too soon to start teasing it)
Killer Instinct 3 (often rumored, never confirmed, with fighting games being "back" since 2009, will it finally become real?)
New Banjo? (Between this or KI3, Rare has to be working on something right? Something not Natal related at least...)
New Itagaki / Valhalla Studios game (finally?)
 
SONY

Killzone 3 (in 3D, oh boy)
Infamous 2 
Little Big Planet 2 
Last Guardian 
Socom 4
Gran Turismo 5 (finally?)
DC Universe Online (we haven't heard anything since last E3) 
Final Fantasy Versus 13 (this one's exclusivity MIGHT be sketchy) 
Final Fantasy XIV
The Agent
God Of War PSP
Pixeljunk Shooter 2 PSN
 
Speculative

Resistance 3 (this one seems almost a given, the timing is right, we know its in development, almost a sure thing for the press conference)
Motorstorm 3 (not a big fan of the franchise, but it doesn't seem like it's going anywhere, and the timing would be right for a 2011 one)
White Knight Chronicles 2 (this has been confirmed to be in development, for japan at least... like Virtual On for 360, more of a TGS than E3 game, but you never know)

New Zelda (this will probably make me buy a Wii again won't it? Goddamn it!) 
Metroid Other M 
NBA Jam
Conduit 2
Epic Mickey
The Last Story
Lost In Shadow
Disney Guilty Party 
de Blob 2
Xenoblade
Arc Rise Fantasia
Sonic Colors Wii / DS
Super Scribblenauts DS
Dragon Quest IX DS
Goldensun DS
Okamiden DS
Pokemon Black & White DS
Ghost Trick Phantom Detective DS
Kingdom Hearts Re:Coded DS
 
Speculative

Pikmin 3 (we know it's in development, announce it already Nintendo) 
Kid Icarus (Rumored for years, will it finally become real?) 
Super Smash Bros. Brawl 2 (like I said earlier, fighting games are back.)
New Starfox (please?)
New Kirby
 
MULTI-PLATFORM

"  Super Smash Bros. Brawl 2 (like I said earlier, fighting games are back.) " 
Super Smash Bros isn't a fighting game.

Tony Hawk R2DE Confirmed

Actually, Versus XIII has NOT been confirmed for E3.  Neither has MGS Rising.

That list looks great. 
It's a damn shame that GB won't have the 'stage show' type thing that ign and gamespot have where they have the developers come and play through their demos and do an interview at the same time. My E3 coverage will probably be gamespot + giant bombcasts. 

" "  Super Smash Bros. Brawl 2 (like I said earlier, fighting games are back.) " Super Smash Bros isn't a fighting game. "

Needs more Agent. So curious to see what the hell it turns out to be.

" Actually, Versus XIII has NOT been confirmed for E3.  Neither has MGS Rising. "

I wanna see some SOUL REAVER :P

" @MysteriousBob said:

" "  Super Smash Bros. Brawl 2 (like I said earlier, fighting games are back.) " Super Smash Bros isn't a fighting game. "

Just what the thread needed...another pointless semantic argument that has been done to death.  Anyway, that's a good, comprehensive list up there. I'm guessing that "New rumored to be a FPS)" was meant to be Respawn Entertainment's game? "

Woah, that's a lot more games than I originally thought there would be!   I can't help but think that a whole lot of those titles are a bit... how to say... 'predictable' though, given that they're all mostly sequels that everyone kind of expected would come out. 
 
The ones from that list that interests me the most are... 
- Portal 2, because while Portal was pretty neat, it was still a two-hour-long tutorial level with only one hour of actual gameplay.   Here's hoping they'll actually make a larger game this time!
- DC Universe Online and Arkham Asylum 2, just because lately I've been really getting into DC comics, and wouldn't mind jumping into a fresh newly-made MMO.
- Virtual On Force, just because I love Sega's style when they actually make good arcadey games, such as Outrun 2006 and After Burner Climax. 
- Metal Gear Solid Rising and Castlevania, because you can't go wrong with Kojima.  Probably.  Even though neither of them really involve Kojima as much as the hype suggests, but...  yeah.
 
Everything else, I'm not really feeling the excitement for.  Pokemon B&W lost my interest when their hyped-up 'REVOLUTIONARY NEW BATTLE SYSTEM' ended up being idle animations, and Golden Sun and Okamiden have a weird sense of familiarity about them that doesn't really catch my attention.

So no  PC list

"So no  PC list "

Saints Row 3 puleeeeze!

Pikmin 3 was already confirmed at E3 08. It just hasn't been heard of since then all that much. Also you're missing Kirby Wii under the speculative list of games for Nintendo. 
@MysteriousBob said:

" "  Super Smash Bros. Brawl 2 (like I said earlier, fighting games are back.) " Super Smash Bros isn't a fighting game. "

Man, that's a lot.

" Pikmin 3 was already confirmed at E3 08. It just hasn't been heard of since then all that much. Also you're missing Kirby Wii under the speculative list of games for Nintendo. 
@MysteriousBob said:

" "  Super Smash Bros. Brawl 2 (like I said earlier, fighting games are back.) " Super Smash Bros isn't a fighting game. "

Then...what genre is it smart guy? "

" @Ace829 said:

" Pikmin 3 was already confirmed at E3 08. It just hasn't been heard of since then all that much. Also you're missing Kirby Wii under the speculative list of games for Nintendo. 
@MysteriousBob said:

" "  Super Smash Bros. Brawl 2 (like I said earlier, fighting games are back.) " Super Smash Bros isn't a fighting game. "

Then...what genre is it smart guy? "

don't let the thread derail into that dude, just ignore that shit. And I added Kirby Wii as speculative, that's a good one "

Nice list, I pretty much agree with it all.

Looks pretty good I'm excited.

added No More Heroes 360/ps3 for outside of japan, something I would love if it happened, also Pixeljunk Shooter 2 PN, Lara Croft XBLA / PSN and Disney Guilty Party (which looks cool actually) for Wii.
 
oh also the new Itagaki game to Microsoft Speculative, he has been working on something for awhile now

moved Killzone 3 from speculative to confirmed, which makes it a bit weird for them to announce resistance 3 AND killzone 3 (resistance 3 isnt official, but it seemed a hell of a lot more likely than KZ3, until today). I guess Sony is going all out

I really want to see the new nfs from Criterion. Hopefully it will be good and not just something holding up the next burnout.

ssx 4!!

Bring on Arkham Asylum 2 and RB3 :D

I'm pretty sure DMC 5 is in development already and being worked on by the Ninja Theory team.  
Not sure if thats good or bad. I didn't care for Heavenly Sword much. 

Most of the speculative lists look believable.
However, for Mass Effect 3, it's not time yet. The craze on Mass Effect 2 hasn't died down yet. It will be too early to reveal anything.
Assuming it comes out mid-2011, the right date to show something should be somwhere around December of 2010 or early 2011.
Same case for Borderlands 2.

BTW, I don't see Rockstar announcing GTA 5. I believe Agent (that PS3 exclusive game) will be more likely.

" I'm pretty sure DMC 5 is in development already and being worked on by the Ninja Theory team.  Not sure if thats good or bad. I didn't care for Heavenly Sword much.  "

" Most of the speculative lists look believable.
However, for Mass Effect 3, it's not time yet. The craze on Mass Effect 2 hasn't died down yet. It will be too early to reveal anything.
Assuming it comes out mid-2011, the right date to show something should be somwhere around December of 2010 or early 2011.
Same case for Borderlands 2.

BTW, I don't see Rockstar announcing GTA 5. I believe Agent (that PS3 exclusive game) will be more likely. "

I only have a 360, but still the thing i'm most looking forward to is more The Last Guardian footage!

Dang that list makes my wallet cry. 

What ever happened to the Resident Evil PSP game they announced back during last year's E3?  I've been keeping an eye out for news on it since then, but there doesn't seem to have been any.  It's a shame if it's been cancelled.  Especially if it was going to be a return to the series' survival horror roots as was implied during the press conference.  Hopefully we'll get some news on it during this year's show.

Demon's Souls 2

Just a suggestion but if you (or someone) could sort that gigantic speculative/multiplatform list by publisher it would be pretty sweet.

" Just a suggestion but if you (or someone) could sort that gigantic speculative/multiplatform list by publisher it would be pretty sweet. "

" Dang that list makes my wallet cry.  "

I looked at the Ps3 and was unfortunately apathetic. Then I looked at multi-platform and I was much happier. Needs more RPGs, though.

New Silent Hill FPS?! What?!

Uncharted news please

" I looked at the Ps3 and was unfortunately apathetic. Then I looked at multi-platform and I was much happier. Needs more RPGs, though. "

" @Rhaknar:  Just makes it easier to read/sort  Eg. Checking which Capcom games will/may be announced rather than looking at a giant list.   But other than that it's  a great list.   I'm pretty sure no one from Bungie is going to be talking about their new game at E3 but you never know with Activision. "

Maybe Max Payne 3? Otherwise thorough list.

" Maybe Max Payne 3? Otherwise thorough list. "

Bully 2.

For Nintendo, add:
 
(Pretty much) Confirmed:
The Last Story
FlingSmash
Xenoblade

Speculative:
Dragon Quest X
Zangeki no Reginleiv EU/NA
DeBlob 2
Ni No Kuni - The Another World (DS)

Also:
 

 New Starfox (please?)  

maybe some kind of teaser for Kingdom Hearts 3 or at least some art