I have 4 boys between the ages of 7-14.
The oldest was OBSESSED with Thomas the tank engine from about age 2-4.
The others played with Thomas a little at about that same age, but they had different favorites.
By age 5, they were completely over Thomas and trains in general.
I think PP brings up an interesting point that maybe if the very young kids didn't have so much Thomas stuff, they would be more into trains as older kids?