What's the best toy train set?

It really depends on how interested they are in trains. My grandsons like the Wooden Railroad Thomas and Friends because they can change the tracks easily and push the trains everywhere, even without tracks. They also enjoy the die cast trains.

For the best model railroad set, I suggest you join your local train club and buy used from the members who have gotten tired of the hobby. Otherwise it can get very expensive.

I still have my 1950s Santa Fe Passenger American Flyer S gauge train set, and it still works.

It was second hand when I got it, and it took a lot of abuse over the years.