Energy is a very poor measure of killing power. A broadhead arrow delivers something like 70 FPE. Nobody doubts it's a pretty effective killer even on very large game.
There have been numerous other measures attempted, but they are all flawed in one way or another.
One that's used quite often is Thornily Stopping Power. On that scale you need
45 for Antelope
50 for Deer
100 for Black Bear (To account for 350- 500 lbs. bear.),
120 for Elk, Moose, Kudu, Zebra, Large African Safari Plains Game
150 for Lion, Leopard, Grizzly Bear, Brown Bear,
250 for Hippopotamus , Rhinoceros, Cape Buffalo, and Elephant.
It's a scale that many safari and big game hunters have used quite sucessfully. You can figure your info here:
http://www.beartoothbullets.com/rescources/calculators/php/thornily.htm
Of course on that scale a baseball delivers a Thornily Relative Stopping Power Scale of 369 (2296 gr @ 141 fps and 2.78 cal).
I haven't heard of many elephant hunters throwing baseballs have you?
The Taylor Knock Out formula is likewise flawed giving a value of 5 for a 50 gr .223 @ 3000fps and a value of 129 for a 96 mph fastball.
http://www.beartoothbullets.com/rescources/calculators/php/taylor.htm?bw=&bv=0&cal=
Stevelyn has it right when he says it's holes in vital organs that kill. The rest of it is just trying (poorly) to quantify how we cause those holes to happen.