Depends on my mood, honestly. I mean, I think it's sexy when two women are together, but its rarely something I'd like to jerk off to. I think that's more of a fantasy of younger men, and one that was popular in 90s culture a lot more than it is now. It came up a lot in pop culture in the 90s because two women being together has always been more socially acceptable than two men.
Anyway, I'd say the whole fantasy was ruined for me when I actually did have sex with a lesbian and it was...awful. haha. I guess, she'd technically be bisexual, but I was the only man she'd ever been with has been ever been with so I think she's a lesbian who had a strait phase. haha. She just had zero clue on what to even do with a penis, it was kind of cute actually, but not a very enjoyable sexual experience overall. haha.