The Leo 2 has seen combat in kosovo with the germans (but only had one fire fight and that was taking out two serbs with AKs in a lada) and is on Op's in Afghanistan with Canada and the Danes. You are right that the Leo 2 has not seen tank on tank combat but M1A1/A2's shooting up 30-40 year old MBT's in Iraq with total air cover has not tested them to their limits yet. I think its a draw until the M1 or the Leo 2 go up against a gen 3 MBT in combat.
No one has any idea what the Abrams has. The material the skirt armor is made out of is still classified to this day.
You can't claim "top spot" just because a tank does well in field tests and does well in a war game. Murphy's Law has a funny way of taking tests and games, and throwing them back in your face where the metal meets the meat.
So a Leo 2 took out Serbs with AK's? So could a Sherman, anything with armor thick enough to make an 7.62x39mm look like a BB could.
Afghanistan maybe starting to be regroup and recoup for the Taliban again, but it is a far, far cry from the streets of Iraq, sure you run into some guys throwing bottles or rocks, but when was the last time that a Leo 2 got caught at a four way and was being bombarded by RPG's and mortars?
Op's is a broad spectrum, even tanks on peace keeping mission do Op's.
And in ODS some Abrams sustained some hits from Iraqi armor. And if you put air support in the the scenario you make the argument moot, because then the air is supporting the M1, making it even more of a beast to contend with.
The Abrams numbers are pretty darn good, 8,500 produced. I have no idea the production numbers of the Leo 2 but I don't think its even close to the M1's, but I could be wrong so don't quote me on that.
Then the argument about reliability and fuel consumption are redundant. 90% of the M1's power pack can be removed without total breakdown of the system. Ok so sand would eat the blades of the turbine, it was fixed by putting a coating on them and using a finer filter.
Fuel consumption, ok sure 1 mpg isn't the best, but when your unit has a support unit two and even three times it size, then fuel comsumption becomes moot. In a combat zone, US support units, normally outnumber combat units. This is the exact reason we where able to fly across France and bash through the hedgerows like we did in 1944, our logistical chain was superb, and we where able to keep control of the skies.
So what it all boils down to is what I said before. A tank is no better than the supporting arms it is supporting. So when you compare the two, the M1 just takes the cake.