The thing is, Luke hasn't made her happy for a long time. Chris didn't make her unhappy, Luke did, and Lorelai went to Chris to feel better. (Which wasn't the best idea while she was still in a relationship.) Maybe Lorelai isn't right for either of them, but Chris has grown up a lot, and he seems to know Lorelai a lot better than Luke does. I have to vote Chris. But Luke isn't a bad guy. It wouldn't be the end of the world if they ended up together, although he would have a lot of apologizing to do.
Chris doesn't know Lorelai at all as an adult! He knows her as a 16 year old girl. I'm not even going to reiterate how well Chris must've been in tune with Lorelai to sleep with her that night, when she was clearly an emotional basketcase. Chris has made Lorelai unhappy several times during the duration of the show. But, hey if you really want Lorelai to be with a guy she doesn't love, just because Luke screwed up once, then that's your prerogative. I personally don't see how anybody that truly cares about Lorelai as a character could possibly want her with Chris. Especially after having watched Partings. I can only come to one conclusion: If you saw Lorelai say Luke was the only guy she's ever loved, if you saw her tell Luke she loved him twice, and if you saw the absolutely stricken, miserable look on her face the next morning when she realized what she'd done with Chris, and still want her to be with Chris, then you really don't care about her. I'm not trying to be harsh, but that's just how I feel.