I met a Christian businessman who is very active in ministry (ordained, too) who looks like he is in his 70s, and his wife looks maybe late 30's or early 40's to me. She could just be young look, but there is a large age gap. He was the president of a large conglomorate at one time, he is friendly, has a very likeable personality, seems very personable and humble. He's accomplished a lot in both business and ministry. I can see how could have attracted a much younger woman. I don't know if he was married before, a widower, or married late, or how long they have been married.
I can understand being creeped out, especially if the one partner is really young when you see them together. But if they are both adults part of me wants to say, "Way to go" to the guy, and nudge him with my elbow for being able to attract a younger woman.
I think it's a cultural thing on our part. In some cultures an age gap is acceptable or even expected. It's not a sinful thing. Isaac was probably 40 or older, and Rebecca was probably a teenager. She was up and about planning and scheming for Jacob while Isaac was old and blind, though. That's a concern. I know when I wanted to marry my wife, who is about three years younger than me, I loved her so I was concerned as to whether I'd be good for her, or would marrying me somehow mess up her life.

If you love a woman, you'll think about her and what will happen if you are old when she is young or if you die. I'm not saying it's wrong to marry like that. If the man is older but he has a lot to offer the younger woman, it may be a 'fair' deal to marry. It's possible for an older spouse to really love a younger spouse, too.
I think it's creepy to see an older woman with a really young man. If he's all grown up, I don't want to throw stones over it. I just think why would he want to be with an old woman when he could be with someone his own age. But people have different preferences, needs, and desires.
Morally, I'd be more concerned with two teenagers who turn 18 going off and eloping against their parents' wishes than with an older man marrying a younger woman when the families are consenting and approving. I'm also more concerned about people getting divorced and remarrying contrary to Christ's teaching within their own age bracket than with widowers and people marrying for the first time when the age difference is large. It would be better for an 18 year old to marry a 90 year old than to commit adultery, even if the idea is less appealing on so many levels physically and emotionally.