I personally think that a lot of people downplay the disadvantages of the T-34, the 2-man turret and lack of radio would be crippling in practice, allowing competing units to service many targets (with a smile!) in the time it takes a T-34 to service one. You can compare gun vs. armor and try to make a judgement based on that, but if the opposing commander never sees you tank because he's buttoned up with poor optics and trying to do 2 jobs at once then it doesn't matter how good his gun or armor are, you can just sidle up alongside them and pop them in the flank.
The question of the "Best", as pointed out by some other people, is really hard to nail down as none of them were really designed to the same specs. Lots of people talking about the Sherman like to compare it to the Tiger, which is obviously problematic because the Tiger is definitely a heavy tank, so it's like comparing a B-17 to a Stuka and saying "Look the B-17 has more guns and a bigger bombload!" The T-34 is the best tank for operating in Russia, the Soviet tankers liked the Sherman except that it's narrow tracks didn't do well in the mud. The Panther is the best tank produced for killing T-34s, sadly it's not the best tank for being produced in sufficient numbers to kill T-34s. The Sherman is the best tank for pumping out a fuckton of highly adaptable tanks that are good enough to be serviceable in combat in pretty much every respect. It's very rare for a clearcut winner to show itself in military equipment as there's ALWAYS tradeoffs that are chosen in the design process, so for a design to come out that's notably closer to perfect than any other isn't likely.
In the end I think it's pretty clear that the T-34 is overhyped and the Sherman is unjustly derided, if I had to choose from the Panther, Sherman or T-34 to be the heart of my military Id choose the Sherman, not because I think it's godly, but because it's failings are relatively minor and if I'm starting from scratch I can give it the Easy 8 suspension and 76mm gun from the beginning, making it a much better tank than the average M4 in WW2 and likely placing it at or above it's peers in overall capability.