Pink seedless grapes. Seasonally available - but by far the best grapes I have ever had. (These still aren't available in Spain.)
Macadamia nuts - (rather an infrequent item) not like other nuts in terms of texture, and a valuable addition to mixed nut combos.
Tomatoes sold 'on the vine' - this has improved the flavour of my favourite 'vegetable'.
Kiwi fruit - again not something I have terribly often, but they are significantly different from anything else, and I am glad they are available.
Filtered milk - eg Cravendale. This one is important. I drink a lot of milk; and this is far better - as well as more reliable and less likely to be semi-rancid - than anything I ever had as a child.
Sausages - are so much improved compared with the low-meat/ high cereal/ high-gristle-content things of my childhood (all that was then available) as to be almost like a different food.
But not everything has changed - for example a major part of my current diet still includes peanut butter, mature cheddar cheese, and Shreddies.