I don't think there'll be playable games from any PS3, "Revolution" or xbo2.
Not playable for the bublic at least, but I'm sure there'll be those staged "playable" games... and a bsod
From sheer quantity it looks safe to say Sony will have the most impressive show, and the PS3
will get the most media attention, that's for sure.
Nintendo might also have a good show, DS has been a success and the mysterious "Revolution" has raised the intrest of many. Nintendo might surprise positively.
Looking past the E3's, the MS showings have been somewhat lacklustre (imo), with not much else exciting but Halo's and every year a new Gran Turismo wannabe game. "Xenon" hardware and demos will be interesting to see, and I'm sure they'll have a next gen Halo concept to show.
I'm just a bit worried based on the recent J. Allard interviews that they concentrate too much hyping the "Live" (old), "HD-Era" (errr..) and "Microtransactions" (not something to fascinate the public).
But Steve Ballmer could still save it for MS with a successor to his "developers" hit, "Steve Ballmer: Microtransactions 2005" (that sounds like some Ibiza summer party super DJ hit mix
)