Mass Effect. Because it's so well thought out, full and rich in personalities and characters (all the way to racial level) and is internally logical. What I mean by that is that the weapons and technology are logical continuations to old ideas but with the new and improved technolgy. And most of all inventions not available to us today in reality are in one form or another based on the application of the Element Zero or Mass Effect as it is called.
There are also realistic limitations to what can be achieved even with the local Unobtanium. For example, space ships don't fire ultra-powerful lasers to light-minutes away because there is no way to cool the spaceships enough. And mass drivers, while the word of the day and highly effective, can be repelled with moderate energy expenditure by using the Mass Effect to create a anti-kinetic shield. Hence ship combat, as described, becomes knife-fighting with short-range low powered lasers, fighter technology (and laser point-defense), missiles (to swarm the point defenses and cause damage by radiation) and broadsides upon broadsides of mass driver rounds being fired upon the other. This continues until either the lasers/missiles do enough damage or the other ship loses shields or one side decides to retreat. And all the while both try to cool their ships down as fast as possible to keep firing at maximum rate and keep maneuvering for the best angle of attack.
So, everything runs around the Mass Effect in neat little circles, logically following one another and the only one thing you would need to accept the universe as possible is the existence of element zero. Everything else would follow.