So, as long as they are equally treating everyone as a sex object? And it isn't really true. There are plenty of males in the ME universe that aren't sexed up. Joker? Garrus? Wrex? The only female I can even think of that isn't in a form fitting suit, with large breasts is the female version of Wrex. Even the girl who needs a special breather has a nice body in spandex.
I guess if one of your definitions of a sex object is merely wearing tight clothes, sure. By that logic though, is every character in Apocalypto a sex object because almost all of them are wearing nothing more than loincloths basically? The point I was making is that the women are no more scantily clad than the men and that at some point it's just part of the aesthetic or the period.
There's plenty of ME woman who are presented without their sexuality figuring as a large part of who they are. For some of them it does become evident as you become better friends (or romance them of course) but it's not a significant part of their presentation - Liara, Ashley (though she does get a makeover), Tali, Chambers, Traynor, Kasumi, Samara. Yes, they do have breasts and yes many (all?) of them wear tight clothing. I guess if that is your sole criteria, then there's not much you can do about that though. I think the devil is in the details.
How do you define a sexed up male? They almost all have the tight clothing and bodybuilder bodies. That seems pretty analogous to "form fitting suit with large breasts". Even Joker is pretty jacked.
Ultimately I think sex appeal is comes down to much more than body and dress, even in a game. Sure, Miranda is sexed up. But so are some girls (and probably guys) in my office, they put in the effort because they want to look or feel a certain way. Those girls are Miranda, and Miranda is those girls. It's just realistic and human to have some dose of it. Even then though she's strong, smart, very family oriented and selfless. It's not like she's just there for decoration; she's a complete character and sex appeal is but one facet that feeds into that.