I was waiting for someone else to do it.  Microsoft and Sony threads have already been started.  Nintendo usually has a really good showing for 3 reasons, they are so secretive the rest of the year, they usually pick some major third parties stuff to show off in there own booth, and they don't go to TGS (Though they usually get invited for a speech).

My Predictions:

Smash Bros. Online will be officially re-announced.

Mario Galaxy and Smash will get dated.

Some big announcement with a more sophisticated DS-Wii connectivity features.  Details on demos or new game-play.

Some new nintendo IP that is more mature (along the lines of Metroid or Fire Emblem maturity) will be announced.

FPS with online announced, not Metroid. (Red Steel 2? New 3rd party IP?)

20+ Touch Generations games shown off. :) Yippie! (That was sarcasm)

EA and Ubi will be present at pre-show event with major title announcements.

What I would like to see (within reason):

A strategy/rts title.

An online RPG, a Dungeon Crawler would be nice, but a MMO would nicer.

A 2d platformer using motion tech.

A well produced flying game (Heatseeker, Blazing Angels, and Wing Island all played really well but had bad presentation) maybe Star Fox or Star Wars.

More beat/shoot-em ups like Marvel Ultimate Alliance and Alien Syndrome.

Some more good Touch Generations games within the 20+ shovelware.

I'd actually prefer they show less at E3. I don't think they have a whole lot to gain by showing all their cards.

I think they will reveal the gun attachment to coincide with Resident Evil U.C. and it will be playable. I would like them to show videos of either New Zelda, Mario Kart, Icarus, or Pilotwings. Or maybe all of the above. I also would like Metroid to be playable and be compatible with the gun attachment. That would be enough to carry them until next year.

My Predictions:

Smash Bros. Online will be officially re-announced ( Yeah, I expect them to show 5-8 characters, stages, etc, and to have a playable demo)

Mario Galaxy and Smash will get dated. ( I think one will get dated, the other one during a Nintendo conference later this year or TGS)

Some big announcement with a more sophisticated DS-Wii connectivity features. Details on demos or new game-play. ( It should happen, the demo thing)

Some new nintendo IP that is more mature (along the lines of Metroid or Fire Emblem maturity) will be announced. ( I think Disaster already fills that...but well, according to IGN, there is something like that on the way)

FPS with online announced, not Metroid. (Red Steel 2? New 3rd party IP?)
( Red steel is already known to be online...I actually don´t expect big 3rd party FPS annuncements until next year)

20+ Touch Generations games shown off. :) Yippie! (That was sarcasm)
( Lets hope they are fewer ganes,,,)

EA and Ubi will be present at pre-show event with major title announcements.
( Spielbers EA project, maybe something else, and Ubi will show RS2, and maybe something more)


What I would like to see (within reason):

A strategy/rts title. ( We already have BWII and FE)

An online RPG, a Dungeon Crawler would be nice, but a MMO would nicer.
( Don´t hold your breath)

A 2d platformer using motion tech. ( That would be nice, wonder why anyone has tried it).

A well produced flying game (Heatseeker, Blazing Angels, and Wing Island all played really well but had bad presentation) maybe Star Fox or Star Wars.
(Pilotwings ir rumoured to be in dev, even for pre-order in Gamespot. I think SF will be announced next year, or late this year, they really need to make it better than SF64 to put the franchises back in the map)

More beat/shoot-em ups like Marvel Ultimate Alliance and Alien Syndrome.
(Probably from 3rd parties)

Some more good Touch Generations games within the 20+ shovelware.

Also, I`m expecting a new pokemon game, that plays more like a traditional RPG, to make it more enjoyable than the last consoler versions.

A new Kid Icarus, it would be play like Zelda, with some twists obviously.

A Nintendo RPG, not in the "younger" lines of Earthbound, more like FF.

Camelot announces Golden Sun 3 for Wii.

20GB harddrive, cheap price.

At least 4 RPGS announced for Wii, specially from Namco. More to come in TGS.

Mario Kart Wii announced in a trailer form, or maybe with a playable level. Looks as good as the arcade, maybe better.

Animal Crossing announced, far bigger than the other versions, allow for much more people visiting villages. May become something like HOME.

And finally, a new DOnkey Kong platformer is shown in a trailer, said to be released in late 08 or early 09.

No Zelda, No F-Zero, No Star Fox, No FE for this year.

My "wild" predictions are that Final Fantasy Chrystal Chronicles will be an online game, it will integrate with the DS version of the game and will be the sleeper hit of the show; Nintendo will show off three completely unconventional games which will make everyone in the audience question their appeal (two of these games will go on to sell millions of copies worldwide); and a Lucasarts starwars lightsaber game will be displayed which seems very interesting but has many flaws at the early stage of development (it will show up again at E3 2008 looking far more polished and entertaining).

Beyond that I would say that Disaster: Day of Crysis will surprise people at how high of quality it is; I say this because Nintendo buying the company reminds me of how Nintendo bought Retro prior to them releasing Metroid Prime.

diegomoroco, I wish you could decide what they'll show at E3, cause you mentioned all the Games I'd love to see, especially Golden Sun and a new DK platformer.

I would also love to see a new Wave Race with Motion Control.

Just think of all the things at last year's E3 they showed that we still haven't seen again yet. They could show any number of things this year.

Oh, and they'll be at TGS this year too.

Personally, I'm not expecting too much, 'cause I know that anything new they do show I'm not likely to see 'till Xmas 2008 anyway.

@diego, why do you think nintendo won't show FE, it's already released in Japan for a long time, feb this year actually. Also according to Wikipedia the US release date is November this year.

As for E3, a spokesperson of Nintendo Germany has claimed Mario Kart Wii will be released this year, and more information will follow at E3. Unfortunetaly there isn't any claims of this on the english wikipedia site, just the dutch one:

http://nl.wikipedia.org/wiki/Mario_Kart_Wii

I highly doubt this information to be true, but I do think E3 will tell us more about Mario Kart Wii. Here's a translation of what the site says:

Mario Kart Wii is the tentative title for the latest part in the Mario Kart series and was announced for the Wii. According to Patrick Nagel (Marketing manager for Nintendo Germany) will there be information available during the E3 Media and Business Summit in Santa Monica on 11 July 2007. He also claims that Mario Kart Wii will be available before 2008 in Japan, North-America and Europe.

ROLE PLAYING GAMES!!! My sweetest dream would be a Tales of exclusive and a Level 5 Role Playing Game for the WII.... *oh boy*. But I will probably be highly dissappointed on that level (ironically enough)

I certainly hope NOT for online Final Fantasy Crystal Chronicles, can't stand online RPG games.

I hope Fire Emblem launches in the same month as SSBB instead of Mario Galaxy, I don't want to have to buy 2 new games in the same month. ;)

Crystal Bearers is mainly a single-player RPG with multiplayer options, from what has been said.

And Konami is working on an un-named Wii RPG, as well as From Software an un-named Wii Action-RPG.  And Namco hasn't said ANYTHING about their "Sword of Legendia" that was announced back in E3'06. :(