Put me down in the 'Seth Green must be Joker' column.And Sam Worthington...
... had better be sent to Pandora for real just to make sure he stays out of this

Anyhow, while my initial reaction is "but it won't be my Shepard(s)", I should be able to get past that.The chances of seeing a Shepard with biotic or tech skills are rather low (and the chances of a fully Renegade Shepard or a female Shepard are less) but given that there are plenty of other characters to show off the other powers (including the
Most Common Superpower ) I think that will be okay. Though it might be a little more interesting to make Shepard an Infiltrator or Vanguard rather than Soldier so there's a bit more variety in the main chracter's combat. Wouldn't bother me too much.
Actually, I hope we get a Paragade character: mostly Paragon with a bit of Renegade fun thrown in (like the occasional punchout of journalisticly inclined individuals).
As great as it could be to see the Mass Effect universe in full cinematic glory (including Mass Relays, the Cidadel, Sovereign, use of biotics, all the different alien races, the Normandy, and best of all, Tali) I'm not sure how much of the plot can fit into the length of one movie. I expect they'll drop out all the side missions and all or most of the sidequests (seriously, they could make another two movies worth of deleted scenes, of which one and a half movies would be pretty boring stuff...) and of course all the walking/driving and elevator scenes would be cut down to a few minutes as required by any dialogue that is needed between combat scenes. And of the main missions, they'll probably skip over many of the 'less important' parts which means a lot of the minor background characters will be passed over entirely. I just hope they don't have to make any radical changes to the story to make it fit.
(Actually they'll have to have a little bit of side-mission stuff to introduce Cerberus)
As cool as this could be, the 'not my Shepard' issue may mean it's better making the movie about a sidestory or something like the First Contact Wars (which would be epic regardless). But I can see why using the existing 'action hero' that Shepard is, is likely to attract more $.
Anyhow, it could be very good, or very very bad. I guess we'll see. (And they'd really better not mess up Tali.) (And the aliens had better not look like humans with costumes on.) (And yeah, they could seriously mess up the Asari if they're not careful.) (And Ashley had better be saved over Kaidan.) (And please, NO love interest for Shepard.)
Just realised this will mean live action husks and creepers. Ewwwww. We better see Jenkins die, btw.
I think that's enough rambling for now.