When sliced bread was first sold in 1928, it was advertised as "the greatest forward step in the baking industry since bread was wrapped". So the best thing before sliced bread would have been wrapped bread.
I'm kind of thinking of inventions that were made shortly before sliced bread. Steam engines made the industrial revolution possible and gave us the railroad, so that was a relatively recent invention that really changed things. Cars and refrigerators had already been invented, but became popular about the same time sliced bread was invented.
Beauty, love, music, unsliced bread, beer, wine, blue jeans, the thrill of the hunt, the bliss of ignorance, the taste of a first kiss, hummus, maple syrup, bacon,and hydrogen-filled zeppelins. Nothing else is better than sliced bread.(IMHO)
On a serious note possibly penicillin and vaccines to eradicate many of the serious illnesses like mumps and measels that were in the not too distant past killers of children and adults alike, Marie stopes, the ability to make fire, and lots of other stuff. On a silly note -unsliced fresh out of the oven bread, OMG - chocolate, soft toilet paper, believe it or not I remember the days when we had cut up newspaper on a string in the downstairs loo and Black prince toilet rolls in the bathroom, it was like greasproof paper and had to be crunched up to be anywhere near effective, I kid you not. Wellington boots and cling film, how did we ever manage without cling film?