I understand you are hurt, but it is just your ego that is hurting. So what if she has had a better lover? Has she had a better husband? A better listener? A better friend? Someone who has cared about her as much as you?
She had been drinking which could explain the increased emotion and ensuing tears of this friend that she had lost. And maybe she thinks he was a better lover that night coz she has idealised it, knowing it was one-time only. She has been having sex with you for so long she may have forgotten how it was right in the beginning. One night stand sex can be very different from relationship/love sex.
Bottom line is she is married to you and loves you. My partner isn't the best sex I have ever had and I am not his. We have openly told each other this. Both of our 'bests' have been with flings where the physical chemistry was dynamite but we had no other connections with these people. I prefer to have the kind of sex I have with my partner now coz I love him and it isn't just based on animal attraction. 'Best' sex is a bit of a grey area IMO.
Like MerryH said if you really do want to elevate yourself to her best lover maybe ask her why that was so good for her and can you do anything to make it like that for her (if you are game enough to ask).
Some people are drains and some are radiators... Keep clear of the drains and hug the radiators!