Yeah, Michael this is kinda what got me thinking about this question. I myself put in lots of fruit trees / shrubs (25+), many of which have proved to be disappointing to say the least. I think most of this issue comes from giving individual trees enough care at the right time, as your efforts become so much more dispersed. My most dependable and highest yielding trees have been the full sized ones, with dwarfing varieties not worth the effort in my opinion. You end up giving them as much
water and fertilizer as full sized trees, and they never seem to really reach that more independent stage (the full sized trees seem to be better at fending for themselves for their nutrient and water). Another bit of misinformation I got while starting out was distances on planting them, the idea being that if you put them closer together they will remain smaller. In my
experience this just often stresses one of the trees out, if not both, especially during extended dry spells (no real rain here for around three months). Irrigation during these times (I'm hand watering, not drip) seems to be more about keeping them alive than keeping them growing. So, from this 10 year adventure, I'd have to say my favourite species for productivity and ease are -
Loquat - early yielding (roughly around Sept / Oct here), a named variety it gives big fruit and a long season, and is dependable for yield.
Strawberry Guava - have this growing in a built in
concrete tub, been my most dependable highest yielding fruit.
Feijoas - get a named variety and you'll have a great fruit, large and flavourful, and drops them when they're ready to eat. Best thing is birds leave them alone.
Apple - double grafted, full sized tree, bears amazingly well, needs thinning out for larger fruit.
Peach - birds don't seem to pester this too much, bears great fruit though good yields only every second year.
Plums - massive crops, only problem is that for blood plums to get a reliable pollination you need to get a multi-graft.
My most disappointing - (I think mainly due to the above points I mentioned, but also throw in the intensity of our summer sun / heat)
Hazelnuts, Almonds (savaged by sulfur crested cockatoos), Mulberries, Currants.
My main point would be go full sized, multi-grafted species, give them ideal plant spacing, get used to bird netting, and be ready to remove those trees that fail to impress. If it's not looking likely after 2-3 years (poor growth, disease, etc) rip it out and try something else. Of course these points are more for those in my situation of trying to grow fruit in a suburban block, rather than the orchard situation.