In no order:
Cortana (Halo): She may not have a physical form, but she's still rather easy on the eyes, intelligent without being condescending, and I can carry her around on any small electronic device so that wherever we're going I only have to buy one ticket or pay one cover charge.
Quistis (FFVIII): Even if they make a better couple than with Rinoa, Squall doesn't deserve her.
Jade (Beyond Good & Evil): She's good with kids (not that I want any, but it's still a nice virtue), tolerates virtuous Quixote-types, and is into photography.
Sonia (Ninja Gaiden II): While her in-game model doesn't live up to her original character design, she's still got that Sarah Jane-type disposition I find myself going for.
Kunoichi (Samurai Warriors): She's a little bit flaky and detached, mistakable for callous, but has that rather lively quality, the kind that you can't stay mad at or have a bad day around.