A friend of mine and I were discussing parallell universes, and he wondered what would have happened if George Washington had caught a stray bullet or just slipped and broken his neck early on. Was there a backup that the young country could have rallied behind? Who would have been a good draft pick?
The wiki article on the Continental Army provides links to the major generals and brigadier generals in the command structure, who are the probable candidates:
This will sound insane, but–Benedict Arnold.
He was extremely talented, & a very capable military commander. And he was considered for Washington’s post.
Treason only came later, after he was turned down. His pro-British wife worked on him awhile, first.
Hmmm, I would wager GW wasn’t close to the best American commander. If I remember correctly, he had a pretty poor record when he served in the British Army during the French and Indian War, and lost or charitably “pushed” just about every battle he was in for the Revolutionary army.
In such discussions (with Arnold being mentioned very favorably, as Bosda notes), the name I’ve seen mentioned, and with something of a consensus behind it, is Nathanael Greene.
Arnold is a pretty good candidate. He won the battle of Saratoga, after all.
Washington’s record prior to the war was irrelevant to his record during it. He did make mistakes – big ones like the Battle of Long Island – but he learned from them and toward the end of the war was far and away the best general out there.
This all depends upon what you mean by “best general.” If you are talking tactics during a battle, Washington often failed in that area. If you mean strategy during a specific campaign, he was much better at that. If you mean overall leadership of troops, such that they will do what you ask of them regardless of the conditions, Washington was at the top of his game (see Valley Forge).
Also, a lot would have depended upon when Washington had been killed. Early on, it would have been a disaster, as one of the major-generals would have been promoted, and they were all four pretty hopeless, as later action showed. Later on, it’s possible that someone with more energy and brains could have been promoted, though note that Gates was in charge in the South originally, and it took the disaster at Camden before Greene was given command.
This is probably IMHO or GD but I think IRL the likely second pick early on would have been a disaster - the worst of all possible picks:
I think there was a “Charles Lee Moment” for all of 1776 until his capture in December for sure … (and maybe even for a short time after he was exchanged until the Battle of Monmouth in mid-1778 but Washington’s qualities were more in evident by then).
Especially early on many saw Lee as the most qualified General (seeing experienced as equaling qualified) plus early on Washington looked shaky in command and if Washington had been killed in the early times- I think likely Lee would have taken over. In fact, he was trying to stab Washington in the back with congress to replace him…one of the many reasons (his foolishness at Monmouth being the best reason why) he would have been a bad #2 (but I think he more than likely would have been)
Washington made some huge mistakes in his career, but it’s worth noting that he only ever made any of those mistakes once, a truly rare trait in any person, much less a military commander.
Washington’s main tactical trick was that he was one of the best Retreaters of his day, which sounds like a backhanded compliment until you realize how difficult it is to maintain organization of a fighting force while also retreating under fire (if they all just break ranks and run, it’s no longer a retreat, it’s a rout, and usually exaccerbated by enemy cavalry running the disorganized men down rather than being fended off by organized ranks of men). He never entered a battle during the American Revolution that he didn’t have a way of exiting with his force intact. Also, one of the biggest muck-ups that he was involved in during the French And Indian War, Braddock’s Defeat, was arguably caused largely because General Braddock didn’t listen to Major Washington’s advice on how to persue a campaign in the region, along with various intercolonial politics.
That said, the best generals for taking Washington’s job would probably be Benedict Arnold, Nathaniel Greene, and perhaps a short list of other officers (Von Stueben and Lafayette were both skilled officers, but neither were Americans, so that would be problematic). There was similarly a list of BAD choices for guys to take over, including the aforementioned Horatio Gates, who spent more time trying to get George Washington’s job than he did actually trying to DO his.
This guy would get my vote. Not only was he very compitant during the war, but was called upon by Washington (as president) to lead up the American Army after the war to fight the Indian War in the Ohio Territory after other commanders failed misrisbly.
Ah, good old Mad Anthony Wayne. I live within minutes of the Fallen Timbers battleground, and one of the local school districts is Anthony Wayne Local School District. We like the guy. 
Odd note–the Pre-Crisis Batman continuity establishes him as one of Bruce Wayne’s ancestors.
Daniel Morgan. Did a mini-Cannae at Cowpens.
Israel Putnam was a very good general. But his historical reputation suffered because he was involved in some retreats (mostly due to circumstances beyond his control) and because he incapacitated by a stroke in 1779.