Lorna, I do think you are setting yourself up for a fall here if you don’t learn to adjust a bit from this black and white thinking. Let’s say you meet the love of your life in the next year or so. Chances are he’s going to be at least 30 years old. He is either going to have slept with quite a few people, or he’s going to have had quite a lot of sex with a few people within LTRs. You are never really going to know if you are "the best" he’s ever had in terms of earth-shattering sex. If he’s the one for you, then he’ll understand your personality well enough to tell you that you are because he loves you. It’s naive to think you "know" that the sex is going to be really good in advance.
When I met my husband at around the same age, initially the sex was… fine. We both came every time but it wasn’t earth-shattering and I was disappointed because we absolutely fancied the pants off each other and were a perfect match intellectually, humour, looks (yes, I agree they are important)… but actually I think we both wanted it to be "perfect" so much that we were possibly trying a bit too hard (in a way you don’t bother with a fling which can be a good thing). After a month or so it all clicked and then some, and I’ve never looked back nearly a decade later. If we sat and thought about it could we say in all honesty that we didn’t have a sexual experience with someone else that still stands out? Probably not, but it honestly only matters if you let it. I wouldn’t ask as I wouldn’t want to torture myself and actually there would be no point as he’d never tell me if that were the case anyway.
There will be some things about your ex which were perhaps a bit "better" in all areas of life, and the same will go for him. You will drive yourself mad if you even begin to go there and waste precious time worrying about it when you should be making the most of each other. You are not the most special woman in the world, you are not the most beautiful or the most sexually skilled, the funniest, nicest, most intelligent... The right man for you will make you feel that way and you should take care of his feelings and make him feel that way too, because it’s never going to be perfect but if you let go of all that shit it could be as near as much.