I know it's not realistic for most aliens to look essentially human, but neither is FTL travel or many other things from Star Trek. However, I think that keeping the Klingons as they looked in TOS would've been better, than their transformation into grotesque monsters in the films and series' afterward.
My reasoning is that when the villains look like monsters, the audience dismisses them as monsters and sees them as unquestionably bad. However, if they looked like you or I, it's easier for the audience to identify with them, which makes stories more compelling. I feel the same way about Romulans, they should've stayed more or less identical to Klingons (Sarek played the first Romulan on screen IIRC) instead of adding those triangular forehead bumps.
Thoughts?
The "Elites" of the Halo series were basically inspired by the Xenomorph from the "aliens" franchise. The basic idea is, take a xenomorph, trade its acid blood and funky reproductive system with with a plasma rifle and a powered armor. They have a menacing, predatory appearance that only gets worse in later incarnations as you get to see them in more detail (upper and lower mandibles filled with teeth, etc).
And yet, they make the transition from enemies to allies halfway through the second game and pretty much stay good guys (mostly) throughout the entire rest of the franchise. Arguably, they actually get MORE alien the more their depiction develops and evolves, even getting their own language, their own culture, their own religious styles. By the time you get to Halo 5, The Arbiter is basically a gold-plated monster who fights on your side.
A similar thing happens in Mass Effect, except that the racial dynamics there are all over the place; most of the antagonists are grouped by ideology or organization and not by species, which means your enemies are defined literally by what unfirom they're wearing and NOT by what planet they're from. So you have the six foot Krogan that are basically anthropomorphic snapping turtles; they're huge, they're violent, they're freakishly strong and annoyingly hard to kill, which is also why the Krogan warrior(s) you recruit for YOUR squad are often your most valuable teammates.
And there's the Star Wars universe, which has one of the most diverse galaxies in any film franchise anywhere, and depicts members of various sepcies fighting in various organizations at various times; there, again, what side you're on actually depends more on what emblem you're wearing on your shirt than what species you were born into.
I hate to say this, but Star Trek's (and fandom's) smug self-assessment as being progressive and open-minded is a bit of a self-delusion. Star Trek has ALWAYS been quick to supply racial stereotypes as proxies for personality traits on the assumption that any particular character can ultimately be reduced to the sum of his cultural norms. Compare this with Mass Effect where the "warrior race guy" Krogan (who are so similar to the Klingons that
Michael Dorn actually voiced one in Mass Effect 2) can be found working as bouncers, technicians, mercenaries, shipping clerks, pilots, botanists, shamen, farmers, hunters, politicians, taxi drivers, and (in one particularly poignant case), standing on a corner reciting bad poetry at his girlfriend. Yes, they have racial/cultural traits
that define alot of their background, but they definitely can't be reduced to that background in any meaningful way. You'll see racist krogan, hungry krogan, bored krogan, krogan that think humans are sexy, krogan that think humans are tasty when sauteed in hot sauce, krogan who just want to settle down and have a couple of hundred kids, and krogan who want to kill everything on a particular planet because the planet is ugly and smells bad.
I would be surprised and impressed if Star Trek managed to depict the Klingons as a vibrant, dynamic civilization with its own layers and dimensions, maybe acting as parallel to our own cultural norms and making us look at ourselves and think "Maybe there's more to us as a society than I really thought about?"
