The amount of people here talking out of their asses is absurd.
The Sherman was an excellent tank, where it's strengths were. Its primary strength was outstanding reliability. German tanks would break down like flies moving anywhere, whereas the Shermies would go on and on. Plus, if a Sherman engine was knocked out or did break, they could change the engine on the spot, whereas German tanks had to be taken back to shops in Germany just to put a new engine in.
The Sherman crews quickly learned speed is their combat asset. When a Tiger would be well positioned, they could usually move around to it's sides and get good shots. Sherman guns could punch the Tiger's side armor fairly easy at close to medium range. Its pretty easy to sneak up to tanks because if the Tank Commander if forced to be buttoned up, the visibility to the sides of the tank is terrible. In a combat situation, you probably wouldn't hear the Sherman engines off to the sides either.
I read before that of 120 assorted Panzer III's and Panzer IV's, they were the mobile reserve unit for the area, and in moving the 50km to the front, only 35 of them made it. That is not acceptable. It usually isn't that bad for those tanks, however.
King Tigers and Tigers may be the best armored/gunned tanks, but their reliabilty sucked even worse. I read somewhere of the first 10 King Tigers to drive to the front from the railroad tracks (not far...can't remember actual distance) only 2 of them made it. They were extremely slow cumbersome beasts. However, well positioned, they could do extreme damage.
As someone forementioned... you hit a tank with enough shells or artillery and chances are the crew will surrender as the shock from all the hits will cause nausea, deafness, puking, and extreme headaches.
Overall the best tank which I haven't mentioned is definitely the T34... it had a decent gun, sloped and adequately thick armor on all sides, and easy to produce. The Russians could make thousands of them with relative ease. Same for the Sherman. German tanks were all much more complicated and much more expensive to make.
The Panther tank was the best German tank overall...but it wasn't as good overall as the T34. Sure it could knock out a lot of T34's, but you could probably make at least 10 T34's in the time it took to make 1 Panther. Panthers had OK reliability, but when repairs were needed, it was far more difficult than it was for a Sherman.
Oh, and reguarding Micheal Wittman, he was extremely lucky in taking out that British column with his buddies. They almost caught him, but not quite. The British were all out of their tanks on a break...
Oh, and reguarding morale... German tank crews were of extreme high quality most of the time, and were usually better than their Allied counterparts (especially the Russians).
As for the best tank of modern times, its the M1A2 Abrams with the only relative competition being the Leopard Mk... well whatever model their newest is on to now. They have a lot of different models. The newest Merkava's, Challenger's, and Leclerc's are also very good modern tanks.
I hope that made grammatical sense... I'm tired and was writing off the top of my head. Oh, and I'm 15 .