Fruit tree maintenance

Five years ago I planted a Morello cherry, a Stella cherry, an Egremont Russet apple, and a greengage, I don't remember the name of the variety.  The two cherries are hardly any bigger than when I planted them, but for the last three years I've had a modest crop from each of them, no more than half a pound of fruit.  The apple and the greengage have grown a lot bigger, and flowered, but produced scarcely any fruit.  They are all in the same place and received the same attention.  I've never pruned any of them, might this be where I'm going wrong?  Or am I just being impatient?