I definitely regret selling the 728i. It was the right thing to do at the time and the new owner loves it and treats it like a baby which is great to see.
The only other car I really miss is my Mk1 MX5. Had it for a few years and loved it but got a cheap Z3 and thought it was better because it had a BMW badge and leather seats! Big mistake. I got rid of that Z3 and now have the nicer one but I’d swap it in the morning for that same MX5!