1. What kind of realism are we talking about here? "Realistic" in terms of our real universe's physics and human behaviors? Or realistic in terms of the literary universe of Star Trek around which the game's features are being developed?
How do you determine the degree of realism of, say, warp drive?
2. What if what's important isn't so much realism as internal consistency?
I can handle warp drives and magic spells... but having them in the same gameworld with no explanation of how such a thing could be would knock me right out of the game experience. It's not that either of these fails the "realism" test -- it's that there's no internal logic; stuff obviously just got thrown into the game arbitrarily by a designer who was much more focused on "game" than on "world."
That's not just a snubbing of gamers who care about story. (Although it definitely is that.) It's also a missed opportunity for developers to make their gameplay more fun by giving it a logical foundation. A logical story creates ideas for gameplay, and gameplay expresses the story. This then creates more gameplay ideas, and so on.
And when all the gameplay action fits consistently into a gameworld, the entire play experience will feel more distinctive to the player. In a time where players have ever more choices of which MMORPGs they'll invest their time and money in, that is not a trivial point.
So I ultimately come back to the point I've been making: gameplay brings in the players, but it's the gameworld that retains the long-term players. A gameworld that's both deep and consistent generates better gameplay.
As MUD1 designer Richard Bartle put it in an online interview with Iron Realms CEO Matt Mihaly:
Progenitor [Richard] says, "The thing about being worldly is that if you have a rich enough world then you automatically get a gamey world too, if you don't stand in the way of it."That doesn't imply a realistic world, but I think it does imply a world that's internally consistent with an established body of lore.
Progenitor says, "So paradoxically, if you want a virtual world that's a good game, you should aim to make it first and foremost a good world."