Hella Yuri Curation

[Miakoda]

I saw that you were making a Curated list of Yuri friendly games on Steam (unless I got this wrong)

If you don't mind a few other suggestions:
Always Sometimes Monsters (you can choose to play as a female, and have a female love interest)
http://store.steampowered.com/app/274310/

Choice of Deathless (a text game, but you can play as female, and romance two females)
http://store.steampowered.com/app/318310/

I also don't know if you want to include Sims 3, but it does allow same-sex marriages.

There was a game recently released called Enola. I haven't played it myself, but you play as the titular character, Enola, and "you must survive a macabre world conjured up by the tortured memories of her love, Angelica"
http://store.steampowered.com/app/263520/

Finally, there is The Yawhg. You don't have control of romances, but some of the random encounters, it is possible for your character to get intimate with females (like an orc, or a prostitute). This may not fit the criteria of your list.
http://store.steampowered.com/app/269030/

Your list included Fallout 2, and Fallout 3. You might wish to add Fallout New Vegas. While there isn't romances per se, you can flirt with females, and lesbians do exist in game (Veronica comes to mind), not to mention the Cherchez la femme Perk gives a few interesting dialogue options with females in game.

You may wish to keep an eye out for Roommates by Winter Wolves Game. While it isn't officially out on Steam yet, I know it passed Greenlight

Something that may be a bit of a stretch for your list, but you may look at Tropico 4 and Tropico 5. You can make a female President, and there is an edict which allows for Same-Sex marriages. Not that your character engages in this herself...

[hanako]

I'm not sure if I missed this post at the time or if you checked a bit outdatedly - most of those are already in. (Probably I was slow in looking here.)

I haven't personally played Choice of the Deathless yet so I was holding off on that until I had a chance to look at it, but it'll probably go in at some point.

The Yawhg I'm less certain about, since as I understand it, not only is that content not very fleshed out or important storywise but you won't always encounter it even if you try to go looking for it.

[Miakoda]

I'm not sure if I missed this post at the time or if you checked a bit outdatedly - most of those are already in. (Probably I was slow in looking here.)

I haven't personally played Choice of the Deathless yet so I was holding off on that until I had a chance to look at it, but it'll probably go in at some point.

]The Yawhg I'm less certain about, since as I understand it, not only is that content not very fleshed out or important storywise but you won't always encounter it even if you try to go looking for it.

Actually, most of my suggestions came before you got them later on the list today, but obviously you found them through other means.

Most Choice of Games...er...games...allow you to dictate whether you are female or male at the start, and what love interests you have. Some of them are quite well written. I hope a few more show up on Steam (I've gotten them from their other sources). Take Tin Star...it is possible to romance a female gunslinger, or a Mexican condessa in the old West. And the writer does take into account the gender of the player; it isn't just a simple substitution. I was quite amazed the writer knew of a Boston Marriage...it makes me want to tackle writing a supernatural Western with a lesbian influence.

And for the Yawhg, I did say it was random, and rather tangential. So, I can understand it not being included on your list.

[Miakoda]

These may already be on your radar, but if not, you may consider the following two games.

1. Roommates - Winter Wolves Game
http://store.steampowered.com/app/317300/
There is one GxG romance in the game (and personally, my favorite romance of the whole bunch).

2. Thieves' Gambit: Curse of the Black Cat
http://store.steampowered.com/app/328550
From the same people who did the Herofall Trilogy, or Choice of the Deathless, this is a text game where you can play as a female jewel thief, and there is a chance to romance a lady in game.