But the only lesbian character I saw that seemed to be like a titillation was Samantha. And even Samantha had more character flaws and sympathy from my side than the generic Steve.
Of course, the fact that only ManShep (and automatically, by the extension FemShep who didn't romance her) got to really know her character, not FemShep who was in relationship with her (her players actually got much less content, mostly when it comes to important, character-building dialogues), strongly suggests that she was from the beginning created with straight men in mind, not lesbians. Steve may be "boring", but his sexuality as a gay man was always treated with full respect and he wasn't for straight yaoi fans' pleasure.
by the way: I only talk about Bioware games. Most other games don't have gay characters at all, and lesbians primarily for the reaons you mentioned.
Fallout New Vegas had perks that allowed gay and lesbian, as well as straight male/straight female conversations with certain NPCs. And guess what, lesbians got significantly less such conversations than gay men, not to mention that their options usually just directed to conversation you could achieve anyway by passing some attribute test, while most gay male conversation options had special content.
It's really starting to remind situation of lesbians and gay men in other media, where gay men are treated as "the real deal", while all the others are pushed aside and ridiculed. According to GLAAD reports, there are more gay male characters in TV than the whole LBT combined. And their sexuality is generally treated with respect, while overwhelming majority of lesbian characters just have to have sex with men, and usually look like they enjoy it, reinforcing incredibly damaging homophobic myths about lesbian sexuality. Interestingly, many such storylines come from gay men as showrunners or headwriters. Few months ago, when "lesbian sleeping with a man" trope happened in "Hannibal", gay showrunner even used his sexuality to silence the criticism from lesbian audience.