That is not correct. The data sheet that I compared between the two shows the same pin out. You can google the datasheet and compare. May be I am missing what the previous guy here was saying but I don’t see any difference in the pin out. The collector current in 2222 is more than 3904 so that part is correct. At least on the Fairchild semiconductor datasheet the 2222 collector current is 1A and the 3904 is only 200mA. I did try to follow the inventor kit guide so you have to just make sure that if you are using 3904, you only get 200mA out from it not more. If you use the 2222, I am guessing you probably can get more.
http://www.fairchildsemi.com/ds/PN/PN2222A.pdf http://www.fairchildsemi.com/ds/2N/2N3904.pdf