Wesker might be. The movie version kinda teeters a bit it seems, well at least Wesker from Afterlife.
Chris I don't think is gay or bi. I think he like Alice in the movies, has been consumed by his fight against Umbrella that he just doesn't have time for that. He's obsessed, but I think he and Jill might have had a relationship, we just aren't let in on it.
Leon is clearly not gay. He has the hots for Ada and Hunnigan.
Claire seemed to be crushing on the older guy from Resident Evil Degeneration, so I doubt her game version is gay. Claire from the movies however; I've entertained the idea somewhat. I thought for a second that she might have a thing for Alice.
The others on the list I'm not too sure about? I was thinking of a couple of guys from the game series and these are the ones who come to mind as being possibly gay....
Ramon Salazar
Lord Saddler
Yoko
George from the Outbreak Series
Jessica (Bisexual)
Raymond
Alfred Ashford (Bisexual)
Those are the others whom for one reason or the other, made me question their sexuality, not that it matters either way. It's just fun to dig deeper and know the characters in and out.