J.-
My son liked the Thomas stuff for awhile, but then didn't care that much about them. There are 2 main problems with Thomas, they are pricey and there are many different sets that don't interact. So, we started our son on one set and when birthday's came along, some got the right set, some got other kind and they don't work together.
Geo-trax he loves! And you can get them anywhere. The kids can build a whole community with an airport and multiple different trains, engines, cars, workers, etc that all work together! Plus they are a good size for little hands. They have remote controlled ones, and ones that you can push around. Plus, you can purchase them just about anywhere. :)
Good luck and have fun!
C.