Books and TV shows that use "realistic" flight also use "time compression" to compensate for these long travel times. For example, a book might read, "Commander, I'm going to get some much needed shuteye. Wake me when we are just outside of range of the enemy vessel." The book then spends a couple of sentences talking about the captain's restless sleep which is over way too soon as a comms calls him to the bridge six hours later.
I'm not a huge fan of time compression in a game unless it's something like a submarine game where time compression is used on the map screen while you wait for a contact. One way to avoid time compression is to add a new technology to the "old" Newtonian thruster technology - jump drives. Space Engineers has this, allowing me to perform a wormhole / space folding jump to get in range of a target, at which point I can then engage in "Newtonian" combat (though SE has speed caps like all other games). There's actually a fun gameplay aspect to this, because if I don't have coordinates to the target, I need to make a "blind jump", which means calculating (or guessing) the vector and distance to jump to bring myself in range of an enemy ship. This may take a few attempts, each one followed by a drive recharge and spool-up period. However, I do like this, because not only is it fun, it's plausible as well.
But on the topic of X4, I honestly don't know why Navigare is saying this is a Newtonian physics game... It's less Newtonian than Elite IMO, but on the other hand there are technologies in this game (artificial gravity, inertial dampeners, etc) that help explain why it's less Newtonian, so that makes the flight model easier to swallow. I actually like X4's flight model more than ED, but I would never say it's more realistic..
