I was biased, because my parents are only 2 1/2 months apart. This one guy who creepily flirted with me until I ghosted him was 6 years older, and I thought that was too old for me.
My best friend, the oldest guy I ever had a crush on, is 4 years older than me. The woman who beat me to his hand and is dating him is more than 10 years younger than him and 6 years younger than me. She's 22, he's 32. That's one of the reasons I was unbearably heartbroken for a couple months after I found out. I never expected any of his college-age coworkers to be viable candidates to spend their lives with him.
I'm friends with two other people whom are dating each other, and I think they're 14 years apart. They seem to be each other's type, though.