Ah the classic "war-winner" argument: I agree to some degree to what you said the T-34 did make a big impact on the war as there were always replacements, however it is important to consider technological advantage or superiority as well. The T-34 was a tank of desperation for desperate times which means it recieved few modernizations or model reworkings/replacements to keep the technological edge, instead everything was kept simple for mass production to rebulid a crippled tank force after 1941. Its greatest strength "production and simplcity" was its greatest weakness which the Germans quickly exploited with their generally better designs not talking about the Panther or Tiger (overkill) series but about the Stug III F-G and Panzer IV G-J series which provided the Germans with unparalleled tank firepower and armor superiority from 1942-1944 against their Soviet counter-parts. In spring of 1944 when the T-34/85 finally cameout ( well on the battle-field) it only served to shorten the techincal gap in firepower (the T-34/85 did not replace the T-34/76 in ww2) its anti-armor properties being inferior to comparable designs such as the Panzer IV and the Sherman 76. It's armor was left almost unchanged (turret armor was only changed) from earlier designs. Both of these failing allowed The Panzer IV and Stug designs to maintain a their superiority at long ranges (as well as optics,ect.) which was the ideal German method to dealing with Soviet tanks. While the T-34 was produced enough that it could ultimately sustain the heavy losses inflicted upon it by the Germans there are many battles in the Ost-front that have been won or adavnces halted/repelled due to "technogical superiority" as well which is why to get a nice solid "BEST TANK" comparison technogical superiority needs to play a major part in the tank in question especially when comparing a vehicle to a German tank design : My pick :
Allies: Sherman 76 or Firefly (because in may ways better than the T-34, it also served in most fronts of the war)
Axis: Stug III/Pz IV or Panther (they do no meet production of T-34 or Sherman but they were the more highly produced German vehicles).