We have been married over 20 years. The first 10 or so my wife was very jealous. I conditioned myself not to pay attention to other women and certainly not talk about them. Even after she started to get past the jealousy issues, I continued to be silent, even evasive with direct questions about who I thought was sexy. Not saying you are jealous, but his past indiscretion may have him in a similar place. When I am not thinking, I sometimes continue to do that now even though we are well past that issue, waiting for the other shoe to fall is a hard habit to break. She gets a kick out of it when I do it now and we can both have a good laugh. Every day it gets easier to leave that habit behind and often share, unsolicited, who I think is sexy.
Another thought. He may be like my wife. I love Julie's game idea, but my wife would beat me 100 - 5. Why? Because she can rule a guy out on looks, but almost never thinks a guy is sexy until she has a conversation with him. For her, personality, brains and voice are what turns her on, your husband may be similar, who knows. I can literally never tell who is going to turn her on. I have thought many times that a guy would be a match for her or that a guy had no chance, based on looks, and usually I am wrong.
Final thought. When we first started sharing who we thought was sexy, I was still using the perspective of "looking for a mate" even though I wasn't. That may sound odd, but it dawned on me, when I was dating I looked through the prism of "mate chemistry" not "playmate chemistry." When you are looking for a life partner you are looking for more chemistry, very few people match up for that. I had to shift my focus back to my early dating days when I was just looking for a good time, still picky, but not same degree of chemistry. I am not looking to share everyday of my life with a playmate, so I can overlook things that would matter if I were. The problem was, at first I did not even realize I was doing that. I am not sure I made a lot of sense there, but for me it made a lot of difference. If your husband is still in that mind set, it could be part of the problem too, no one meets his ideals, so no one turns him on.