*If you ask the question in 30 years the people who are 18 or so now will probably say Rishi Sunak (if he's around long enough) purely because, as the OP stated, he was PM during their best times. Not because he's a great PM but because it was their best times - young, beautiful, carefree (for five minutes ), able to travel, party with friends, go to university. No ties, few responsibilities, self belief.
As I said upthread, Thatcher was PM during my best times, but my best times had nothing to do with her, they were to do with being young, free, single and the world being my oyster*
I asked some 18 year olds at a party recently and they talked about climate change, sewage, Brexit screwing up study/travel/science, the things they can’t have/do because mortgages have gone up and potentially never being able to have children or a home of their own because wages are so low
It’s certainly possible they’ll say Sunak was PM during the best of times for them…
But only if things continue to get even worse.