I prefer the M-1 Garand (.30-O6) or the M-1A - also known as M-14 (.308/7.62mm) with a match grade barrel. Ammunition is heavy to carry in the field, but I think they did the job better. General Patton called the Garand the greatest weapon of war ever invented for a reason.
Also, due to complaints, Ranger medics were at one time being issued HK MP5s instead of that horrible M-16 carbine. I loved that little beauty, it was so easy to carry on a sling with the heavy medic pack, gave me great close quarters firepower and I could have it right there slung over my shoulder at the ready when treating a patient.
I agree. I've never had much faith in the 5.56, despite what the critics said. I don't think that the ammo weight is as big a factor as it was in previous conflicts because the soldiers did most of their travelling in vehicles and didn't have to worry about packing 10 lbs of ammo in a 40 mile a day hike.
The 5.56 may have adequate stopping power at ranges inside 100 meters, but beyond that it isn't nearly as capable as the 30-06 or 308. Many of the engagements in the desert were well beyond the effective range of the 5.56 and the bad guys with the AK-47's had a clear advantage.
Rather than trying to make the M-16/M-4 a "one size fits all solution", I've been saying for a while that perhaps the better solution is to have troops train with two guns: an MP-5 (whether in 9mm, or modified for a 5.56 round) for urban warfare and situations where it's unlikely you will be engaging targets beyond 50 yards, and a 7.62 NATO calibre weapon for long range work