Since no one else has mentioned it, I don't think...
...I will point out that the M16 and AK-47 aren't really contemporaries. I mean, sure, variants of both have been used since the 60's, BUT....
The AK-47 design has about ten or eleven years on the M16. It is based on the Nazi MP-44 of World War II. So, essentially, the bare-bones, basic design of the AK-47 has been around for over fifty years, and is still aces today. Not bad.
Not that the M16's record is shabby. It's been in constant production since the mid-60's, and is used 'round the world.
NOW, my personal experience with the M16 is limited to my beater A1 I have in the National Guard (we're talking golden oldie here) and the beater A2 I used in boot camp.
I've never fired my A1 with regular ammunition. For qualification, we only have a pistol range near our armory, so we have to use a special bolt and platic frangible ammunition (blue tip). Most of the time, said ammo works reasonably well, but lemme tell you, it fouls up the barrel like you wouldn't believe. The other ammo I've used is blanks, and let me tell you, if the M16 performed as well with live rounds as it does with blanks, I'd sooner drop it in the lake and take a damned .30-30. It can scaracely fire a full magazine on semi without becoming a single shot rifle (with blanks). I've never fired my A1 on full auto with live rounds. I got to qualify with the SAW last summer, "qualification" was having us shoot SEVEN round belts at a paper target 10 feet in front of us. Had to haul the spare barrels, too, although not only did we not need them, I wasn't issued the oven mits needed to change the barrel.
In boot camp, I had an A2, which worked well for me. It only jammed on the range once or twice, during the three weeks of Basic Rifle Marksmanship. (we didn't fire them much after that) I only fired like two magazines on burst fire. I noticed that "three" round burst was more like one, then three, then two, then four round burst, but hey, who am I to tell the brass any different?
Considering the AR design lacks a gas piston and sprays barrel spooge right back into the chamber (VERY dirty!) it works rather well, actually. It could be worse (see original M16).
I currently own a semi AK clone, so I have experience with that as well. Here are my recommendations for each.
AR-15
-Losen up tolerances
-Make front sight easier to adjust
-If possible, redesign the bolt to not have so many small pieces
-Lose the three round burst. Full auto fire in a rifle is limited in its uses; 3RB has no combat function whatsoever, that I can see.
-Make the #*$@%# handguards easier to take off.
-Start giving M4s to Combat Engineers!
D)
-Shorten the selector switch just a bit, so when it's on semi it doesn't bug the trigger finger of us lefties
-Ambidextrious selector switch (although I'd still use my left thumb to move it)
Avtomat Kalashnikov
-Push Button Magazine release
-Make the front sight easier to adjust
-Leave the adjustment of the rear sight as is (it's so quick) but replace the sight itself with a peep sight
-If possible, incorporate a non-reciprocating charging handle (ever get smacked in the thumb by that sucker?)
-Use of carbon fiber and synthetics to lighten the weight
-Ambidextrious sling loops
-Thicker pistol grip (my personal desire, anyway)
-Better trigger (you can feel the recoil of the AK in the trigger...my finger got tingly, today, after 100 rounds...was kind of unpleasant)
-Make the recoil buffer standard issue (makes it last longer)
Just my $00.02