But merely making synthetics appearing human isn't enough. This is when the narrative doesn't make sense. It branch from accepting a version of alternate life into appropriating them in a single leap. Mass Effect doesn't provide you with enough material to work with the humanized-synthetics narrative and relationship (which is much better explored in Battlestar Galactica, Humans, Blade Runner, Real Humans and even Terminator).
"Humanized-synthetics"? that's totally anthropocentrist and that's not Mass Effect's ending! That's your first wrong step.
Then you are making comparison with other pieces. But here is your second wrong step : your comparison can be valid only if a comparison can be make (which means to see what is in common and the what are the differences to understand how they are different). So here your comparison is useless : saying that X is better than X whitout any explanation doesnt lead us anywhere.
So now let's see your comparison :
-Battlestar Galactica, Humans and real humans are TV series, so you want to say that TV series are much developed than Mass Effect on this point (organics/synthetics). Mass Effect was written like a trilogy of films, not like a TV serie.
-Blade Runner, yes that's easy, because it is a masterpiece and you think that nobody will say that Mass Effect is at the same level Blade Runner is. Actually you're wrong, the level of writing of Mass Effect is as high as Blade Runner is. Blade Runner focused on human and replicant being (identity, life etc...). The difference between organics and synthetics is part of what makes Mass Effect, it is developed but in a different way. If you don't go into details, you know that Blade Runner is a masterpiece because the critics said it (I don't think you know why it is a masterpiece because you wouldn't put Blade Runner close to Battlestar Galactica, Humans, real Humans), but you won't understand why Mass Effect isn't at a lower level. Both Blade Runner and Mass Effect used implicit (in a different way) while TV series work on explicit things because of the audience.
-Terminator, which one? there are films and TV series. There are two masterpieces (Terminator 1 and 2) and the others were made to make money.
So just like that guy who created a topic on synthesis and talked about Mass Effect and Deus Ex as if Mass Effect was supposed to be like Deus ex, you are wrong : Mass Effect is different, the writing is different, you have to understand it to make comparison, or you have to make comparison in order to understand how Mass Effect is different from BSG, etc...
That's the principle of the comparison. Imposing your vision of the writing is irrelevant because you are not talking about Mass Effect but what you think Mass Effect is or what you want it to be.