Which backstory will you be going for this time?

Going for an Earthborn background but with a Paragon path. That way Shepard can start as an underdog who rises his way through the ranks.

Spacer would probably work.  

While I've done the "Spacer/War Hero", given it's my favorite, I have to admit, the "Earthborn/Sole Survivor" resonates different if you go mostly Paragon.
Like a "I refuse to fall to my circumstances" type of mindset.

Colonist/War Hero

I like the idea that Shephard tries to become a "perfect hero" because him feeling like he failed his colony even if he was just a kid.
That is kind of the whole drive through the whole trilogy: Never gonna fail again.
Would also explain the almost suicidal drive Shep has.

Colonist/Ruthless Paragon (Paragade) is my favorite, but I like Earthborn/War Hero and Spacer/Sole Survivor, too.

Earthborn/War Hero I like because of the "came from nothing and proved themselves in the Blitz" thing. The codex entry for personal history in ME1 says that Shepard was on shore leave on Elysium when the batarians attacked. I like to think that she was just pissed off that they ruined her shore leave and that's why she "held the line".

Spacer Shep seems like she's had a pretty good life, not much conflict (possible except being her father's death, if he is indeed dead), adding Sole Survivor to the mix gives that conflict.

Earthborn/ Sole Survivor.

I think...still enough days to change my mind.

Most likely a Spacer/War Hero/Paragon Female solider which is my main character in the original MET and I don't see any real reason to change that in ME:LE.

Colonist/Ruthless

Colonist because my last two Shepards have been Spacer and Earthborn respectively, because it fits the specific Shepard I intend to play, and because it pairs well with Ruthless. And Ruthless because it's way more interesting than the other two reputations.

War Hero kind of just says that Shepard is very heroic and was in the right place at the right time to make a difference, and Sole Survivor just says that they're mentally tough and have been through some shit. The Ruthless reputation refers to actual choices they've made, which informs who they are and what they're capable of on a whole other level compared to the other two.

And depending on Shepard's demeanor in the game, The Butcher of Torfan can be the man/woman they are, can be the person they become out of necessity when things are most desperate, or can be a huge personal failure and mark of shame that they'll spend the rest of their lives atoning for. Which is why I pretty much always pick it.

It kicks ass, and works with everything except a perfectly moral Shepard with a clean record and conscience. And who wants to play that?

Every one of my Sheps have to be born on Earth. My canon Shep is then sole survivor, but I like to pick Spacer once in a while. Ruthless only when going for pure renegade route.

I have to decide whether to play male or female... never mind back story!

My canon Shep used to be Colonist/Sole Survivor but this time I changed it to Colonist/Ruthless as I think it works better with his personality and story.

Colonist is my favorite origin, its linked quest is the best. From there I 50/50 split between war hero/ruthless as they both feel linked to a colonist story. So it kind of feels like your back story is wrapped up. I let the dice decide and got war hero this game.