Comparing T-34 to Tiger and especially to Tiger II is not very fruitful, as they were very different tanks. T-34 was a medium, all-purpose tank, while Tiger I/II were heavy tanks, and should be compared to something like Soviet KV-85 or IS-2. In any event, the original Tiger had 650hp engine, which proved to be underpowered, and was later replaced with a 700hp one; Tiger II and Panther used the same engine I believe. 2.75 gallon/mile fuel consumption was quoted for Tiger I (cross-country), 4.5 for Tiger II (whopping 50 miles on one 860L tank!), and 1.75 for Panther A/G. Don't know cross-country fuel economy numbers for T-34, but the spec road range is about 290mi for T-34/76 (compared to 125 for Panther, 87 for Tiger I and 70 for Tiger II).

Panther tank was designed as a heavy-medium tank midway through the war, to incorporate the best of the T-34 design features, and there's much argument over how good a tank Panther really was. It did have stronger armoment and better armor than the original T-34, although T-34/85 closed the gap some, but it was also heavier and far less reliable/servicable. Like many other tanks, it proved to be more effective in defensive warfare, and the timing of its introduction (early '43) only allowed for one last great German offensive, where Panther didn't exactly lived up to Hitler's high expecations, partly due to early-production manufacturing problems. It was quite successful in subsequent defensive operations though.

Many people like debating the benefits of various tank models based on their technical data. For example, some admire Tiger II as a super-tank, and regard Tiger as the "best" tank of the war, and it's a valid argument. However, a tank that's good on paper is not necessarily an effective tank on the battlefield. Tiger had a great gun and very strong armor, but it was very heavy, wide, slow, espensive to manufacture, hard to maintain and needed too much fuel. T-34 was the opposite of this: light, fast, rangy, compact but with wide tracks, low to the ground, simple and cheap to mass-produce, realiable, easy to fix, and this suited the Eastern Front warfare so much better. Soviets had heavy tanks of their own, and they had their uses (e.g. assault of heavily fortified compounds) but those were never deployed in large numbers largely for the reasons cited above. Soviet commanders viewed a mainstream tank as a vehicle for infantry combat support, a role that T-34 played extremely well, and preferred using specialized anti-tank units and ground combat aircraft for destroying German tanks. The issue of replacing the original T-34 tank with something else was raised repeatedly throughout the war, but the original design was so good, all newer designs got eventually dumped in favor of tweaking the original one.

What is ironic (and not widely appreciated) is that all of the great Blitzkrieg victories of 1939-1942 that German Panzer corps are famous for were won primarily with PzKpfw I-III tanks which were light, fast, and had small guns, and yet German heavy tanks are most known and renowned. French and Polish armies had heavier tanks, but that didn't help them all that much. T-34 was superior to all German tanks as of mid-1941, and heavy KV-1 and KV-2 tanks were very hard for German tanks to disable due to their thick armor. Still, Germans panzers were quite successful in 1941 despite this, although in part because T-34 and KV tanks weren't very numerous at this point. Tiger was only introduced in numbers in late 1942, and Tiger II was never produced in big enough numbers to have a big effect on the war.