This isn't even remotely close to the truth. There's three "sex scenes" if you can even call them that, in Mass Effect. One of them shows
the arm of a female, and that's literally all you see. Another one shows a side view of a female but it's heavily out of focus, and the last one shows maybe a bit of female alien butt (out of focus) for less than a second.
If you really want to see what all the commotion is about, go to Youtube and type in Mass Effect and any of your various sexual terms, and I'm sure you'll be guaranteed results.
It just pisses me off, because I know if I was still a kid and my parents heard about all of these "realistic sex acts" then there'd be absolutely no way I would have been able to play this awesome game. These things just get heavily blown out of proportion, and I'm glad that the gaming industry doesn't seem to really care. Furthermore, to add to the entire thing, all of the "sex scenes" can be completely avoided in the game, and can only be achieved by wooing your partners, in which case the child is most likely already fully aware of sex and is probably old enough to see these scenes anyways.
[Edit] And no, you cannot customize any characters in the game other than your own character. Yes, technically you could make a female, and I guess maybe you can change her bust size, but then again that's nothing new or shocking to this type of genre. Also, it's not a "sex simulation" as there is no interaction by the player, they're merely cutscenes.
Author of the JK levels:
Sand Trap & Sand Trap (Night)